Basics
Cricket is a team sport for two teams of eleven players each. A formal game of cricket can last anything from an afternoon to several days.
Although the game play and rules are very different, the basic concept of cricket is similar to that of baseball. Teams bat in successive innings and attempt to score runs, while the opposing team fields and attempts to bring an end to the batting team's innings. After each team has batted an equal number of innings (either one or two, depending on conditions chosen before the game), the team with the most runs wins.
(Note: In cricket-speak, the word "innings" is used for both the plural and the singular. "Inning" is a term used only in baseball.)
The Field
A cricket field is a roughly elliptical field of flat grass, ranging in size from about 90 to 150 metres (100-160 yards) across, bounded by an obvious fence or other marker. There is no fixed size or shape for the field, although large deviations from a low-eccentricity ellipse are discouraged. In the centre of the field, and usually aligned along the long axis of the ellipse, is the pitch , a carefully prepared rectangle of closely mown and rolled grass over hard packed earth. It is marked with white lines, called creases, like this:
The dimensions are in centimetres (divide by 2.54 for inches).
The Play
The order in which the teams bat is determined by a coin toss. The captain of the side winning the toss may elect to bat or field first.
All eleven players of the fielding team go out to field, two players of the batting team go out to bat. The remainder of the batting team wait off the field for their turn to bat. Each batsman wears protective gear and carries a cricket bat.
The game progresses by the bowling of balls. The sequence of events which constitutes a ball follows:
The fielding team disperses around the field, to positions designed to stop runs being scored or to get batsmen out. One fielder is the bowler. He takes the ball and stands some distance behind one of the wickets (i.e., away from the pitch). Another fielder is the wicket-keeper, who wears a pair of webbed gloves designed for catching the ball and protective pads covering the shins. He squats behind the opposite wicket. The rest of the fielders have no special equipment - gloves to assist catching the ball are not allowed to anyone but the wicket-keeper.
One batsman stands behind each popping crease, near a wicket. The batsman farthest from the bowler is the striker, the other is the non-striker. The striker stands before his wicket, on or near the popping crease, in the batting stance. For a right-handed batsman, the feet are positioned like this:
The batsman stands with his bat held down in front of the wicket, ready to hit the ball, which will be bowled from the other end of the pitch. The batsman usually rests the lower end of the bat on the pitch and then taps the bat on the pitch a few times as "warm-up" backswings.
The non-striker simply stands behind the other popping crease, waiting to run if necessary. The bowler takes a run-up from behind the non-striker's wicket. He passes to one side of the wicket, and when he reaches the non-striker's popping crease he bowls the ball towards the striker, usually bouncing the ball once on the pitch before it reaches the striker. (The bowling action will be described in detail later.)
The striker may then attempt to hit the ball with his bat. If he misses it, the wicket-keeper will catch it and the ball is completed. If he hits it, the two batsmen may score runs (described later). When the runs are completed, the ball is also considered completed. The ball is considered to be in play from the moment the bowler begins his run-up. It remains in play until any of several conditions occur (two common ones were just described), after which it is called dead. The ball is also dead if it lodges in the striker's clothing or equipment. Once the ball is dead, it is returned to the bowler for the next delivery (another name for the bowling of a ball). Between deliveries, the batsmen may leave their creases and confer with each other.
When one bowler has completed six balls, that constitutes an over. A different member of the fielding team is given the ball and bowls the next over - from the opposite end of the pitch. The batsmen do not change ends, so the roles of striker and non-striker swap after each over. Any member of the fielding team may bowl, so long as no bowler delivers two consecutive overs. Once a bowler begins an over, he must complete it, unless injured or suspended during the over.
Another possibility during a ball is that a batsman may get out. There are ten different methods of being out - these will be described in detail later. If a batsman gets out, the ball is dead immediately, so it is impossible to get the other batsman out during the same ball. The out batsman leaves the field, and the next batsman in the team comes in to bat. The not out batsman remains on the field. The order in which batsmen come in to bat in an innings is not fixed. The batting order may be changed by the team captain at any time, and the order does not have to be the same in each innings.
When ten batsmen are out, no new batsmen remain to come in, and the innings is completed with one batsman remaining not out. The roles of the teams then swap, and the team which fielded first gets to bat through an innings. When both teams have completed the agreed number of innings, the team which has scored the most runs wins.
Scoring Runs
Whenever a batsman hits the ball during a delivery, he may score runs. A run is scored by the batsmen running between the popping creases, crossing over midway between them. When they both reach the opposite crease, one run is scored, and they may return for another run immediately. The fielding side attempts to prevent runs being scored by threatening to run out one of the batsmen.
If the batsmen are attempting to take runs, and a fielder gathers the ball and hits a wicket with it, dislodging one or both bails, while no batsman is behind that wicket's popping crease, then the nearest batsman is run out. Specifically, the batsman must have some part of his body or his bat (provided he is holding it) grounded behind (not on) the crease.
The batsmen carry their bats as they run, and turning for another run is accomplished by touching the ground beyond the crease with an outstretched bat. The batsmen do not have to run at any time they think it is unsafe - it is common to hit the ball and elect not to run.
If the batsmen run one or three (or five! rare, but possible), then they have swapped ends and their striker/non-striker roles are reversed for the next ball (unless the ball just completed is the end of an over).
In addition to scoring runs like this, if a batsman hits the ball so that it reaches the boundary fence, he scores four runs, without needing to actually run them. If a batsman hits the ball over the boundary on the full, he scores six runs. If a four or six is scored, the ball is completed and the batsmen cannot be run out. If a spectator encroaches on to the field and touches the ball, it is considered to have reached the boundary. If a fielder gathers the ball, but then steps outside or touches the boundary while still holding the ball, four runs are scored. If a fielder catches the ball on the full and, either during or immediately after the catch, steps outside or touches the boundary, six runs are scored.
The batsmen usually stop taking runs when a fielder is throwing the ball back towards the pitch area. If no fielder near the pitch gathers the ball and it continues into the outfield again, the batsmen may take more runs. Such runs are called overthrows. If the ball reaches the boundary on an overthrow, four runs are scored in addition to the runs taken before the overthrow occurred.
Runs scored by a batsman, including all overthrows, are credited to him by the scorer. The number of runs scored by each batsman is an important statistic.
If, while running multiple runs, a batsman does not touch the ground beyond the popping crease before he returns for the next run, then the umpire at that end will signal one short, and the number of runs scored is reduced by one.
Ways of Getting Out
Here is a full list of the ten different ways of getting out. But first, a few necessary definitions:
The wicket is said to be broken if one or both of the bails have been dislodged and fallen to the ground. If the bails have fallen off for any reason and the ball is still in play, then breaking the wicket must be accomplished by pulling a stump completely out of the ground. If the wicket needs to be broken like this with the ball, the uprooting of the stump must be done with the ball in contact with the stump.
The field is notionally split into two halves, along a line down the centre of the pitch. The half of the field in front of the striker is called the off side, the half behind is called the leg side, or sometimes the on side. Thus, standing at the bowler's wicket and looking towards a right-handed striker's wicket, the off side is to the left and the leg side to the right (and vice-versa for a left-handed striker). The stumps of the striker's wicket are called off stump, middle stump, and leg stump, depending on which side they are on.
When a batsman gets out, no matter by what method, his wicket is said to have fallen, and the fielding team are said to have taken a wicket.
Now, the ways of getting out:
Caught:
If a fielder catches the ball on the full after the batsman has   hit it with his bat. However, if the fielder catches the ball, but   either during the catch or immediately afterwards touches or steps   over the boundary, then the batsman scores six runs and is not out.
Bowled:
If the batsman misses the ball and it hits and breaks the wicket   directly from the bowler's delivery. The batsman is out whether or not   he is behind his popping crease. He is also out bowled if the ball   breaks the wicket after deflecting from his bat or body. The batsman   is not out if the wicket does not break.
Leg Before Wicket:
If the batsman misses the ball with his bat, but   intercepts it with part of his body when it would otherwise have hit   the wicket, and provided several other conditions (described below)   are satisfied. An umpire must adjudicate such a decision, and will   only do so if the fielding team appeal the decision. This is a   question asked of the umpire, usually of the form "How's that?" (or   "Howzat?"), and usually quite enthusiastic and loud. If the ball   bounces outside an imaginary line drawn straight down the pitch from   the outside edge of leg stump, then the batsman cannot be out LBW, no   matter whether or not the ball would have hit the stumps. If the   batsman attempts to play a shot at the ball with his bat (and misses)   he may only be given out LBW if the ball strikes the batsman between   imaginary lines drawn down the pitch from the outside edges of leg and   off stumps (ie. directly in line with the wicket). If the batsman does not attempt to play the ball with his bat, then he may be given out   LBW without satisfying this condition, as long as the umpire is   convinced the ball would have hit the wicket. If the ball has hit the   bat before the hitting the batsman, then he cannot be given out LBW.
Stumped:
If a batsman misses the ball and in attempting to play it steps   outside his crease, he is out stumped if the wicket-keeper gathers the   ball and breaks the wicket with it before the batsman can ground part   of his body or his bat behind his crease.
Run Out:
If a batsman is attempting to take a run, or to return to his   crease after an aborted run, and a fielder breaks that batsman's   wicket with the ball while he is out of the crease. The fielder may   either break the wicket with a hand which holds the ball, or with the   ball directly. It is possible for the non-striker to be run out if the   striker hits the ball straight down the pitch towards the   non-striker's wicket, and the bowler deflects the ball on to the   wicket while the non-striker is out of his crease. If the ball is hit   directly on to the non-striker's wicket, without being touched by a   fielder, then the non-striker is not out. If the non-striker leaves   his crease (in preparation to run) while the bowler is running up, the   bowler may run him out without bowling the ball. Batsmen cannot be run   out while the ball is dead - so they may confer in the middle of the   pitch between deliveries if they desire.
Hit Wicket:
If, in attempting to hit a ball or taking off for a   first run, the batsman touches and   breaks the wicket. This includes with the bat or dislodged pieces of   the batsman's equipment - even a helmet or spectacles!
Handle The Ball:
If a batsman touches the ball with a hand not   currently holding the bat, without the   permission of the fielding side. This does not include being hit on   the hand by a delivery, or any other non-deliberate action.
Obstructing The Field:
If a batsman deliberately interferes with the   efforts of fielders to gather the ball or effect a run out. This does   not include running a path between the fielder and the wicket so that   the fielder cannot throw the stumps down with the ball, which is quite   legal, but does include any deliberate attempt to swat the ball away.
Hit The Ball Twice:
If a batsman hits a delivery with his bat and then   deliberately hits the ball again for any reason other than to defend   his wicket from being broken by the ball. If the ball is bouncing or   rolling around near the stumps, the batsman is entitled to knock it   away so as to avoid being bowled, but not to score runs.
Timed Out:
If a new batsman takes longer than two minutes, from the time   the previous wicket falls, to appear on the field.
These methods of getting out are listed in approximate order of how commonly they occur. The first five are reasonably common, the last five quite rare. The last three methods are almost never invoked.
If a batsman is out caught, bowled, LBW, stumped, or hit wicket, then the bowler is credited with taking the wicket. No single person is credited with taking a wicket if it falls by any other method.
Officials
The game is adjudicated by two umpires, who make all decisions on the field and whose word is absolutely final. One umpire stands behind the non-striker's wicket, ready to make judgements on LBWs and other events requiring a decision. The other umpire stands in line with the striker's popping crease, about 20 metres (20 yards) to one side (usually the leg side, but not always), ready to judge stumpings and run-outs at his end. The umpires remain at their respective ends of the pitch, thus swapping roles every over.
If the technology is available for a given match, a third umpire is sometimes used. He sits off the field, with a television replay monitor. If an on-field umpire is unsure of a decision concerning either a run out or a stumping attempt, he may signal for the third umpire to view a television replay. The third umpire views a replay, in slow motion if necessary, until he either reaches a decision or decides that he cannot make a clear decision. He signals the result to the on-field umpire, who must then abide by it. If the equipment fails, the replay umpire signals no decision. The replay umpire cannot be used for any decisions other than run outs and stumpings.
Whenever any decision is in doubt, the umpire must rule in favour of the batsman.
If the ball hits an umpire, it is still live and play continues. If it lodges in an umpire's clothing, then it is dead.
The game is also presided over by a match referee, who watches from outside the field. The referee makes no decisions of relevance to the outcome of the game, but determines penalties for breaches of various rules and misconduct. In professional games, these penalties are monetary fines.
Arguing with an umpire's decision is simply not tolerated. Anything more than a polite question to the umpires is heavily frowned upon and could attract a penalty from the referee. The most serious misconduct in a cricket match is of the order of a rude gesture to an opponent or throwing the ball into the ground in disgust. Such gross misbehaviour would attract large fines and possibly match suspensions. Penalties for physical violence can only be guessed at, but would possibly be a career suspension.
Extras
Extras are runs scored by means other than when the ball is hit by a batsman. Extras are not credited to any batsman, and are recorded by the scorer separately. The total number of runs for the innings is equal to the sums of the individual batsmen's scores and the extras. There are four types of extras: no balls, wides, byes, and leg byes.
The bowler must bowl each ball with part of his frontmost foot behind the popping crease. If he oversteps this mark, he has bowled a no ball. The umpire at that end calls "no ball" immediately in a loud voice. The batsman may play and score runs as usual, and may not be out by any means except run out, handle the ball, hit the ball twice, or obstructing the field. Further, if the batsman does not score any runs from the ball, one run is added to the batting team's score. Also, the bowler must bowl an extra ball in his over to compensate. A no ball is also called if any part of the bowler's back foot is not within the area between the return creases.
If the bowler bowls the ball far to one side or over the head of the batsman, so making it impossible to score, the umpire will signal the ball as a wide . This gives the batting team one run and the bowler must rebowl the ball. The striker may not be out hit wicket off a wide ball.
If the striker misses a ball and the wicket-keeper fails to gather it cleanly, the batsmen may take runs. These runs are called byes and are scored as extras.
If the striker, in attempting to play a shot, deflects the ball with part of his body, the batsmen may attempt to take a run. Such runs are called leg byes . If the striker did not attempt to play a shot with his bat, leg byes may not be taken. The umpire adjudicates by signalling a dead ball if the batsmen attempt to run when, in his opinion, no attempt was made to play a shot.
Batsmen may be run out as usual while running byes and leg-byes. If, while running either form of bye, the ball reaches the boundary, four byes (of the appropriate type) are scored.
The Bowling Action
The bowling action itself has to conform to several restrictions. The bowler's arm must be straight when the ball is bowled (so no "throwing" is allowed). The ball must be bowled overarm, not underarm.
The difference between 'bowling' and 'throwing': When you throw the ball, the elbow is cocked and used to impart energy to the ball by straightening. When a ball is bowled, the elbow joint is held extended throughout. All the energy is imparted by rotation of the arm about the shoulder, and possibly a little by wrist motion. For a right-handed bowler, the action goes roughly as follows:
After the run-up, the right foot is planted on the ground with the instep facing the batsman. The right arm is extended backwards and down at this stage. The left foot comes down on the popping crease as the bowler's momentum carries him forward - he is standing essentially left-side on to the batsman. As the weight transfers to the left foot, the right arm is brought over the shoulder in a vertical arc. The ball is released near the top of the arc, and the follow-through brings the arm down and the right shoulder forward rapidly.
Bouncing the ball on the pitch is not mandatory. It's usually done because the movement of the ball off the pitch makes it much harder to hit. Unbounced deliveries, or full tosses are almost always much easier to hit, and mostly they are bowled accidentally. A full toss above hip height is no ball, and an umpire who suspects that such a ball was deliberate will give the bowler an official warning. A warning is also given if the umpire believes the bowler is bowling at the body of a batsman in a deliberate attempt to injure the batsman. After two warnings a bowler is barred from bowling for the rest of the innings.
If any rule governing the bowling action is violated, a no ball results.
Bowlers are allowed to polish the ball by rubbing it with cloth (usually on their trouser legs) and applying saliva or sweat to it. Any other substance is illegal, as is rubbing the ball on the ground. Usually one side of the ball is polished smooth, while the other wears, so that the bowler can achieve swing (curving the ball through the air). It is also illegal to roughen the ball by any means, including scraping it with the fingernails or lifting the seam. A bowler who illegaly tampers with the ball is immediately suspended from bowling for the rest of that innings.
The bowler may bowl from either side of the wicket, but must inform the umpire and the batsmen if he wishes to change sides. Bowling with the bowling arm closest to the wicket is called over the wicket, and is most common. Bowling with the non-bowling are closest to the wicket is called around the wicket.
The bowler may abort his run-up or not let go of the ball if he loses his footing or timing for any reason. The umpire will signal dead ball and the ball must be bowled again. If a bowler loses his grip on the ball during the delivery action, it is considered to be a live ball only if it is propelled forward of the bowler. If such a ball comes to rest in front of the striker, but any distance to the side, the striker is entitled to walk up to the ball and attempt to hit it with his bat. The fielding team must not touch the ball until the striker either hits it or declines to do so.
A delivery may also be aborted by the striker stepping away from his stumps, if distracted by an insect or dust in the eye, for example.
Fielding
Field placements in cricket are not standardised. There are several named field positions, and the fielding captain uses different combinations of them for tactical reasons. There are also further descriptive words to specify variations on the positions labelled by simple names, so that any position in which a fielder stands can be described.
The following diagram shows the rough positions of all of the simply named field positions. In this diagram, the pitch is indicated by three '#' marks; the striker's end is at the top. The bowler is not shown, but would be running upwards towards the bottom end of the pitch. The approximate field positions are marked with numbers or letters, according to the key on the right of the diagram. The three marks: '+', '*', and '~' indicate that the adjective shown at the bottom of the list can be used to describe a modification of that position, as shown in the example.
---------------------------------          1  wicket keeper        /                                   \        2  first slip       /          e                h         \       3  second slip      /                                       \      4  third slip     /                                         \     5  gully +    /                                           \    6  point +*~   /                                             \   7  cover +  /                      2                     j  \  8  extra cover + |                     43 1  d                     | 9  mid-off +* |                  5                              | a  mid-on +* |                6       # i      c | b  mid-wicket + |                        #                        | c  square leg +~ |                7       #        b               | d  leg slip |                 8                               | e  third man |                                                 | f  long off  \                  9         a                  /  g  long on   \                                             /   h  fine leg    \                                           /    i  bat-pad     \                                         / +  deep (near boundary)      \                                       /  *  silly (near batsman)       \          f                g         /   ~  backward (more 'up')        \                                   /  eg.          ---------------------------------   j  deep backward square leg
(This picture will be replaced with an inline image when I have time.)
Other modifiers used to qualify positions:
square: close to a line perpendicular to the pitch, through the batsman;
fine: close to a line straight along the pitch;
short: close to the batsman.
The only restriction on field placements is that, at the time the ball is delivered, there must be no more than two fielders in the quadrant of the field backward of square leg. (This rule exists mainly for historical reasons - see the Bodyline section below.)
Sometimes fielders close to the bat wear helmets for safety. When not in use, the helmet (or any other loose equipment) may be placed on the field (usually behind the wicket-keeper, where it is unlikely to be hit by the ball). If any such loose fielding equipment is hit with the ball, five runs are scored, either to the batsman who hit the ball or as the appropriate form of byes. The ball is then considered dead and no further runs can be taken, nor can a batsman be run out.
If a fielder is wearing a protective helmet, and the striker hits the ball so that it bounces off the helmet, he may not be out caught off the rebound. If a ball rebounds from any other part of the body of a fielder, he may be out caught if another fielder (or the same one) then catches the ball before it hits the ground.
Injuries and Substitutions
In case of injury, substitutes may replace any number of fielders. A substitute may only field - he may not bowl, nor bat. A substitute may not keep wicket. A substituted player must return to the field as soon as he is able to resume playing without danger.
If a batsman is injured, he may retire and resume his innings when fit again, so long as his team's innings is not over. If a batsman is too injured to bat when no other batsmen remain to come in after a wicket falls, his innings must be forfeited and his team's innings ends. If a batsman is able to bat, but not run, then another player may run for him. The runner must wear the same equipment as the batter, and performs all his running. The injured non-runner must remain behind his crease at all times when the ball is in play or risk being run out, even if his runner is safely behind a crease.
If a bowler is injured during an over and cannot complete it, another bowler must bowl the remaining deliveries in that over. The bowler chosen to finish the over must not be the bowler who bowled the previous over, and must not bowl the over immediately following either.
A player may not leave the field for injury unless the injury is sustained on the field. An injured player who takes the field may not leave because of his pre-existing injury, unless it is clearly aggravated further on the field.
Adverse Weather Conditions
Play is suspended at the umpires' discretion for rain. Light rain is usually tolerated, though nothing heavier, because of the possibility of damage to the pitch. If the players are off the field, they must remain off until the rain has stopped completely. During rain the pitch is covered with waterproof material to protect it. Often the bowlers' run-ups and an area around the pitch are also covered.
During very windy conditions, sometimes the bails will tend to blow off the top of the stumps. If this becomes a problem, the umpires can decide to play without bails. In this case, the wicket does not need to be broken by uprooting a stump, and the umpires must take full responsibility for deciding, in a reasonable manner, whether the wicket is broken or not.
The umpires signal various events with gestures, as follows:
Out:
When a batsman is out, the umpire making the decision raises one   hand above his head, with the index finger extended.
Not Out:
There is no formal signal to indicate that a batsman is not   out. The umpire can either shake his head 'no' or not signal at all.
Four:
A four scored by the ball reaching the boundary is signalled by an   arm extended horizontally and waved briefly back and forth in a   horizontal arc.
Six:
The Two Forms of Cricket
Cricket is played in two very distinct forms. The first is limited duration, in which a specific number of hours of playing time are allocated and each team plays two innings.
The second is limited overs, in which each team plays one innings of a pre-determined number of overs.
First Class Cricket
First class cricket matches are the most prestigious games, played at a professional level. The top level games are international Test matches, played between countries. There are also domestic first class cricket competitions. First class matches are of limited duration. Test matches will be described first, then any differences for other first class matches will be described.
Test matches are played over five days, with six hours of play each day. Each day's play is divided into three sessions of two hours each, with a 40 minute break between the first two session for lunch, and a 20 minute tea break between the last two sessions. A short drinks break is taken once an hour, or more often in very hot weather. Play usually goes from 11:00 local time to 18:00, although this may be varied if sunset occurs early. The scheduled close of play time is called stumps. Test matches are never played under artificial lighting.
Each team has two innings, usually played in alternating order. Each innings is over when either ten batsmen are out, or the captain of the batting side declares the innings closed (for strategic reasons, more later). When all the innings are completed, the team with the most runs wins. If there is a tie, the result stands (this is rare - it has only ever happened twice).
If by the end of the final day's play all the innings are not completed, the game is a draw, no matter who appeared to be "winning". Thus the strategic importance of sometimes declaring an innings closed, in order to have enough time to dismiss the other team and so win the game.
The order of the innings alternates except when the follow-on is enforced. This can occur if the second team to bat in the first innings scores 200 or more runs fewer than the first team. The captain of the first team may then ask the second team to follow on: to bat its second innings immediately, and defer his own team's second innings until afterwards.
Whenever a change of innings occurs during a session, a ten minute break is taken. If the end of an innings occurs within ten minutes of the end of the first or second sessions, the ten minute break is lost and the scheduled interval is shifted to begin immediately. If the end of an innings occurs within ten minutes of stumps, the day's play ends early.
Test matches are played with a red cricket ball. A new ball is used for the beginning of each innings. The same ball must be used throughout the innings, being replaced only in the following cases:
The captain of the bowling team may elect to take a new ball at any time   after 80 overs have been bowled with the previous ball.
If the ball is lost, it is replaced.
If the ball is damaged, either by the stitching coming undone or the    ball becoming clearly non-spherical, it is replaced.
In cases 2 and 3, the ball must be replaced by a previously used ball of similarly worn condition to the old ball, as chosen by the umpires. If the ball is ever hit so that a spectator gathers it, the spectator must return it so that play can continue.
On each day of play in a Test match, a minimum of 90 overs must be bowled. If the bowling team has not bowled the required minimum by the scheduled stumps time, play is extended until the required number of overs have been bowled.  Whenever an innings ends, the number of overs to be bowled is recalculated, disregarding the number of overs bowled so far during the same day. The required minimum is calculated to be the number of minutes of play remaining, divided by 4 and rounded up. On the last day of play, this formula is used up until one hour before stumps, then fifteen overs are added to the result. If extra overs are bowled before the time one hour before stumps on the final day, then there still must be a minimum of fifteen overs bowled after the time one hour before stumps. All of these conditions are recalculated for time lost due to poor weather, at a rate of one over per 4 minutes of lost time. If a day's play ends early because of poor weather conditions, all calculations are reset for the next day.
If there is heavy cloud cover, the umpires may decide that the ambient light level is too low and that the batsmen may be in danger because of difficulty in sighting the ball. If so, they offer the light to the batsmen, who may agree to leave the field or may decide to play on. If the light deteriorates further, the umpires will offer again. If the batsmen decide to leave the field and the light improves, the umpires make the decision to resume play.
If a fielder leave the field for any reason and then returns during the same innings, he may not bowl until he has been on the field again for as much time as he spent off the field.
Test matches are played in Series between two of the official Test nations. A Test Series consists of a set number of matches, from one to six, all of which are played to completion, even if one team gains an unassailable lead in the Series. Series of three or five matches are most common. Some pairs of nations compete against one another for a perpetual trophy. If a Series between two such nations is drawn, the holder of the trophy retains it.
Non-Test first class cricket differs from Test cricket in only a few respects. A non-Test first class match is usually three or four days long, not five. In a four-day game, the cut-off figure for enforcing the follow-on is 150 or more runs behind the first team. The formula used to determine the minimum number of overs bowled in a non-Test first class match may be different to that used for a Test match; there is no standard regulation.
Non-Test first class competitions are usually round-robins amongst several domestic teams. Other first class matches include single games between visiting international sides and domestic first class teams.
One-Day Cricket
One-day cricket differs significantly from first class cricket. A one-day match is played on a single day. Either a red or a white cricket ball may be used, and play under artificial lighting is common.
Each team gets only one innings, and that innings is restricted to a maximum number of overs. Usual choices for the number of overs are 50, 55, or 60. Recently, an abbreviated form of the games has been developed called Twenty20, with a maximum of 20 overs per innings.  Each innings is complete at the end of the stipulated number of overs, no matter how many batsmen are out. If ten batsmen are out before the full number of overs are bowled, the innings is also over. If the first team's innings ends in this manner, the second team still has its full number of overs to score the required runs. The timing of the innings and the break between them are not regulated.
Whichever team scores the most runs wins. A tied score stands. There is no draw result. If the match is washed out, so that the innings are not played, the game is declared a no-result.
In each innings, each bowler is restricted to bowling a maximum number of overs equal to one fifth of the total number of overs in the innings. Either a single new ball is used for each innings, or two new balls which are alternated between overs. (This is often done with white balls because they wear much faster than red balls.) New balls are never taken during an innings, but replacements for lost or damaged balls are taken as in first class matches.
In case of rain interruption to the first innings, the number of overs for each innings is recalculated so that they will be the same. If rain interrupts the second innings, making it impossible for an equal number of overs to be bowled, the number of runs scored by the first team is adjusted to compensate. The standard adjustment formula now used is the "Duckworth-Lewis method", which is arcane even for cricket aficionados and too complicated to describe here.  There is also a predetermined number of overs that must be bowled in each innings for any result to be considered valid; if this limit is not reached the game is a no-result.
Because of the emphasis on scoring runs quickly, wide balls and high balls (called as no ball) are enforced much more strictly in one-day cricket.
One-day competitions are played either as Series between pairs of international teams, round-robin competitions among groups of international teams, or round-robins among domestic teams. A World Cup one-day competition is played between all the Test nations every four years.
Strategies, Tactics, and Trivia
All of the rules of cricket have been described above, as well as some other information which is not "rules", such as names of fielding positions. The rest of this file concerns other information that is useful to know, but not actually "rules".
Bowling Styles
There are two basic approaches to bowling: fast and spin. A fast bowler bowls the ball as fast as practicable, attempting to defeat the batsman with its pace. If the ball also swings in the air, or seams (moves sideways) off the pitch because of bouncing on the seam, it can be very difficult to play. A spin bowler has a more ambling run-up and uses wrist or finger motion to impart a spin to the ball. The ball then spins to one side when it bounces on the pitch, thus also hopefully causing it to be hard to hit. Fast bowlers are generally used with a new ball, while spin bowlers get more spin with a worn ball. There is also medium pace bowling, which concentrates more on swing and seam than pace.
A swing bowler will hold the seam of the ball at a certain angle and attempt to release the ball so that it spins with the seam at a constant angle. With one side of the ball polished and the other rough, differential air pressure will cause it to swing in the air.
A seam bowler attempts to keep the seam vertical, so that the ball hits the seam when it bounces on the pitch and deflects in its path either to the right or left.
A fast bowler can also pull his fingers down one side of the ball as he lets it go, imparting a small amount of sideways spin to the ball. This can cause the ball to move sideways off the pitch. Such a delivery is called a leg-cutter if the ball moves from the leg side to the off side of a right-handed batsman, or an off-cutter if moves from the off to the leg. A specialist spin bowler can get a lot more spin that a fast bowler bowling cutters, however.
There are two types of spin bowling: off-spin, and leg-spin. Imagine holding a ball in your right hand and, for simplicity's sake, throwing it. If you twist your hand in a clockwise direction on release, then the spin on the ball will be such that when it bounces it will spin to your right. This is essentially off-spin bowling (so called because, to a right-handed batsman, the ball spins from the off side to the leg side). The off-spin delivery itself is called either an off-spinner or an off-break. An off-spin bowler will sometimes not spin the ball so much, putting more pace on the delivery. Such a delivery is called an arm-ball.
Now imagine twisting the ball anticlockwise and releasing it from the palm so that it 'rolls' over the base of the little finger. This gives the ball spin in the opposite direction, so it spins left when it bounces. This is basic leg-spin (because to a right-handed batsman it spins from leg to off). The basic leg-spin delivery is called a leg-spinner or leg-break.
The interesting thing about leg-spin is that if you cock your wrist at various angles you can in fact, with the same basic bowling action, produce spin in different directions. With the wrist cocked a little towards the inside of the arm, you can produce top-spinners. Go further and you actually end up producing spin in the same direction as an off-spinner. A ball bowled in this way by a leg-spin bowler is called a wrong 'un, or sometimes a googly . Probably trickiest of all is a ball bowled with the hand in the same position as a top-spinner, but released from under the hand, thereby gaining back-spin. This ball is called a flipper.
(Mike Whitaker tells me that a flipper is actually bowled from the back of the hand like a normal leg-spinner, but with the forearm twisted outwards, so the ball spins about a vertical axis. I'm not sure which of these is correct, so I'm mentioning both here!)
Mike has also kindly supplied a graphic which attempts to show the arm and wrist action of the different leg-spin deliveries. Sorry for those with only ASCII browsers, but this is too difficult to show in ASCII! For those of you with graphical browsers, the following diagram shows a view of a (right-handed) leg-spinner's arm, from in front (i.e., batsman's point of view). The rotation of the ball out of the hand is the same in each case, with the ball spinning with the seam as an "equator".
So right handed spinners fall into two classes: off-spinners, with their simple off-spin and arm-ball deliveries; and leg-spinners, with their leg-spinners, top-spinners, wrong 'uns, and flippers. Leg-spinners are naturally much more difficult to bat against, because of the great variety of balls they can produce, but they are actually rarer than off-spinners because it is so much more difficult to bowl reasonably accurately with the leg-spin hand action.
For left-handed spin bowlers there is a whole different system of nomenclature!
A left-handed bowler who uses the same action as an off-spinner is called an orthodox spinner. Such bowlers are not uncommon. A left-hander who bowls with the same action as a leg-spinner is called an unorthodox spinner - and these are the rarest bowlers in cricket. The left-handed analogue of the leg-spin delivery (which spins the opposite way, of course) is called an unorthodox spinner. The top-spinner and flipper retain their names. And the left-handed analogue of the wrong 'un is called a Chinaman .
Typical bowling speeds are:
Spin bowler:
70-90 km/h (45-55 mph)
Bowlers also make use of the state of the pitch, which is quite crucial to the game, and is one of the things the commentators look at in great detail before the game begins. Because it's a natural surface, there are usually small inconsistencies in its flatness, hardness and elasticity. Over a multi-day game, or even over a single day, these become more pronounced, so it often gets more difficult to bat as the game progresses. Spin bowlers in particular often find that they get much more spin from an old pitch than a freshly prepared one.
Some of the different types of balls bowled have special names:
Bouncer:
A ball bounced short so that it bounces high, usually chest   height or higher as it passes the batsman.
Yorker:
A ball bounced very close to the batsman's crease. This is   difficult to score from and often gets batsmen out, but is difficult   to bowl without accidentally bowling a full toss.
The different types of shots a batsman can play are described by names:
Block:
A defensive shot played with the bat vertical and angled down at   the front, intended to stop the ball and drop it down quickly on to   the pitch in front of the batsman.
Drive:
An offensive shot played with the bat sweeping down through the   vertical. The ball travels swiftly along the ground in front of the   striker. A drive can be an on drive, straight drive, off drive,   or cover drive, depending in which direction it goes.
Cut:
A shot played with the bat close to horizontal, which hits the ball   somewhere in the arc between cover and gully.
Edge, or Glance:
A horizontal bat shot which pulls the ball around the batsman into   the square leg area.
Sweep:
Like a pull shot, except played with the backmost knee on the   ground, so as to hit balls which bounce low.
Hook:
Like a pull shot, but played to a bouncer and intended to hit the   ball high in the air over square leg - hopefully for six runs.
French Cut:
An attempt at a cut shot which hits the bottom edge of the   bat and goes into the area behind square leg.
Reverse Sweep:
A sweep with the bat reversed, into the point area.
Most of these shots can also be lofted, in an attempt to hit the ball over the close fielders (or the boundary). The batting strokes can be divided into two categories: Straight bat and cross bat. The straight bat shots are played with the bat held close to the vertical, and are the blocks, drives and glances. Cross bat shots are played with the bat held more horizontally, like a baseball bat. These include cuts, pulls, sweeps and hooks.
The following terms are used more informally and are not standard:
Hoik:
A wild swing intended only to hit the ball as hard and as far as   possible, usually with little or no control.
Agricultural Shot:
More Weird Names
If a bowler completes an over without any runs being scored from it, it is termed a maiden.
If a batsman gets out without scoring any runs, he is said to be out for a duck . The origin of this term is unclear, but commonly rumoured to be because the '0' next to his name on the scorecard resembles a duck egg. A batsman out for a duck while facing his first delivery of the innings is out for a golden duck.
The runs scored while two batsmen bat together are called their partnership. There are ten partnerships per completed innings, labelled from first-wicket partnership to tenth-wicket partnership, in order.
A nightwatchman is a batsman who comes in to bat out of order towards the end of a day's play in a multi-day game, in order to 'protect' better batsmen. To elucidate, the batting order in an innings is usually arranged with two specialists openers who begin the innings, then the rest of the batsmen in order of skill, best to worst. The job of the openers is to bat for a while against the new ball. A brand new ball is very hard and bouncy, and fast bowlers can use this to great advantage and can often get batsmen out. So it is harder to bat against a new ball. It is also somewhat difficult to begin batting. A new batsman is more likely to get out than one who has been on the field and scoring runs for a while.
Now, in a multi-day game, it sometimes happens that a team's innings will have only a few men out towards the end of the day's play. If a batsman gets out with about half an hour or less until stumps, the batting captain will sometimes send in a poor batsman next instead of a good one. The idea is that the poor batsman (the nightwatchman) will last 20 minutes and so protect the good batsman from having to make a fresh start that evening and again the next morning. It is essentially a sacrifice ploy. Of course, it can backfire dangerously if the nightwatchman does get out before stumps. The nightwatchman is a tactic that is used about 50% of the time when the appropriate situation arises (which itself occurs perhaps once every 4 or 5 games). It just depends on how the captain feels at the time.
A sightscreen is a large screen positioned on the boundary so that it forms a backdrop behind the bowler, so that the striker can see the ball clearly. Sightscreens are white when a red ball is used, and black for a white ball.
A rabbit is a player (almost invariably a bowler, but sometimes a wicket-keeper) who is a very poor batsman. A ferret is an extremely poor batsman (so called because he "goes in after the rabbits").
The following statistics are recorded:
Batsmen:
number of runs scored, time spent batting, number of balls   faced, how out (and by which bowler and catcher if appropriate).
Bowlers:
number of overs bowled, number of maidens bowled, number of   wickets taken, number of runs conceded (i.e., scored off his bowling).
Team:
extras, total runs, wickets fallen, overs bowled, total at each   fall of wicket.
A single innings scorecard might look like this:
Australia - 1st Innings M. Taylor      c Richardson  b Snell      12 M. Slater      lbw Donald                 57 D. Boon        b de Villiers              68 M. Waugh       not out                   184 A. Border      c Rhodes  b Donald          0 S. Waugh       c Snell  b de Villiers     34 I. Healy       c Snell  b de Villiers      6 S. Warne       run out                    35 M. Hughes      st Richardson  b Cronje    10 C. McDermott   b de Villiers              41 G. McGrath     lbw de Villiers             9        Extras                             16        Total   141 overs          10 for 472  Bowling - South Africa O   M   R   W A. Donald       40   5  106  2 F. de Villiers  37   7   85  5 R. Snell        32   3  126  1 C. Simons       15   0   82  0 H. Cronje       17   2   73  1 FOW: 25, 99, 164, 164, 225, 238, 315, 345, 446, 472  The abbreviations are: b bowled by c caught by st stumped by O  overs M  maidens R  runs W  wickets FOW  fall of wicket
The team score is usually given as "(number of wickets) for (number of runs)" in Australia. In England, New Zealand, and some other countries it is given as "(number of runs) for (number of wickets)". Bowling figures are sometimes printed in shortened form, for example: Donald 40-5-106-2, de Villiers 37-7-85-5, etc.
The partnership scores can be seen from the differences between successive fall of wicket scores.
Good performances are considered to be:
A batsman scoring 50, or 100, or multiples thereof.
A partnership adding 50, or 100, or multiples thereof.
A bowler taking five wickets in a single innings.
A bowler taking ten wickets in a two innings match. (This is   an excellent performance and a relatively rare feat.)
A bowler taking a hat trick, i.e., three wickets in three     successive balls (perhaps in different overs). This is even more rare.
Each of these tasks is usually greeted with enthusiastic applause from the spectators. The crowd also usually applauds significant events such as: any wicket falling, a six, a four, a good over from a bowler (one that the batsmen have great difficulty playing safely), a good athletic effort from a fielder to gather the ball, the innings total reaching a multiple of 50.
The number of runs scored in an innings average about 3 per over for a first class match, and 4 per over in a one-day match. The variation in these numbers can be quite large, differences of up to one run per over being not uncommon. In a first class match, a captain makes his decision on declaring the innings closed based on the remaining time in the match and the size of his team's lead.  He will try to allow as much time as possible to bowl the opposition out, while ensuring they do not have enough time to score enough runs to win.
Over a single player's career, the two most important statistics are:
Batting Average:
The aggregate number of runs scored divided by the   number of times the batsman has been out. The higher, the better.
Bowling Average:
The aggregate runs scored against a bowler divided by   the number of wickets taken. The lower, the better.
Each of these averages is kept separately for Test cricket, first class cricket in general, and one-day cricket. A batting average above 30 is very good, 40 excellent, and 50 is legendary. Mention must be made of the Australian batsman Sir Donald Bradman, whose career average was a record 99.94, far and away the greatest batsman ever to play the game. A bowling average below 25 is considered excellent.