The ball is a hard leather-seamed spheroid, with a circumference of 22.9 centimetres (9.0 in). The ball has a "seam": six rows of stitches attaching the leather shell of the ball to the string and cork interior. The seam on a new ball is prominent and helps the bowler propel it in a less predictable manner. During matches, the quality of the ball deteriorates to a point where it is no longer usable; during the course of this deterioration, its behaviour in flight will change and can influence the outcome of the match. Players will, therefore, attempt to modify the ball's behaviour by modifying its physical properties. Polishing the ball and wetting it with sweat or saliva is legal, even when the polishing is deliberately done on one side only to increase the ball's swing through the air, but the acts of rubbing other substances into the ball, scratching the surface or picking at the seam are illegal ball tampering.
A bowler reaches his delivery stride by means of a "run-up" and an over is deemed to have begun when the bowler starts his run-up for the first delivery of that over, the ball then being "in play". Fast bowlers, needing momentum, take a lengthy run up while bowlers with a slow delivery take no more than a couple of steps before bowling. The fastest bowlers can deliver the ball at a speed of over 145 kilometres per hour (90 mph) and they sometimes rely on sheer speed to try to defeat the batsman, who is forced to react very quickly. Other fast bowlers rely on a mixture of speed and guile by making the ball seam or swing (i.e. curve) in flight. This type of delivery can deceive a batsman into miscuing his shot, for example, so that the ball just touches the edge of the bat and can then be "caught behind" by the wicket-keeper or a slip fielder. At the other end of the bowling scale is the spin bowler who bowls at a relatively slow pace and relies entirely on guile to deceive the batsman. A spinner will often "buy his wicket" by "tossing one up" (in a slower, steeper parabolic path) to lure the batsman into making a poor shot. The batsman has to be very wary of such deliveries as they are often "flighted" or spun so that the ball will not behave quite as he expects and he could be "trapped" into getting himself out. In between the pacemen and the spinners are the medium paced seamers who rely on persistent accuracy to try to contain the rate of scoring and wear down the batsman's concentration.
The patrons, and other players from the social class known as the "gentry", began to classify themselves as "amateurs"[fn 1] to establish a clear distinction vis-à-vis the professionals, who were invariably members of the working class, even to the point of having separate changing and dining facilities. The gentry, including such high-ranking nobles as the Dukes of Richmond, exerted their honour code of noblesse oblige to claim rights of leadership in any sporting contests they took part in, especially as it was necessary for them to play alongside their "social inferiors" if they were to win their bets. In time, a perception took hold that the typical amateur who played in first-class cricket, until 1962 when amateurism was abolished, was someone with a public school education who had then gone to one of Cambridge or Oxford University – society insisted that such people were "officers and gentlemen" whose destiny was to provide leadership. In a purely financial sense, the cricketing amateur would theoretically claim expenses for playing while his professional counterpart played under contract and was paid a wage or match fee; in practice, many amateurs claimed somewhat more than actual expenditure and the derisive term "shamateur" was coined to describe the syndrome.
It is generally believed that cricket originated as a children's game in the south-eastern counties of England, sometime during the medieval period. Although there are claims for prior dates, the earliest definite reference to cricket being played comes from evidence given at a court case in Guildford on Monday, 17 January 1597 (Julian calendar; equating to 30 January 1598 in the Gregorian calendar). The case concerned ownership of a certain plot of land and the court heard the testimony of a 59-year-old coroner, John Derrick, who gave witness that:
Cricket flour may be used as an additive to consumer foods such as pasta, bread, crackers, and cookies. The cricket flour is being used in protein bars, pet foods, livestock feed, nutraceuticals, and other industrial uses. The United Nations says the use of insect protein, such as cricket flour, could be critical in feeding the growing population of the planet while being less damaging to the environment.
The wicket-keeper and the batsmen wear protective gear because of the hardness of the ball, which can be delivered at speeds of more than 145 kilometres per hour (90 mph) and presents a major health and safety concern. Protective clothing includes pads (designed to protect the knees and shins), batting gloves or wicket-keeper's gloves for the hands, a safety helmet for the head and a box for male players inside the trousers (to protect the crotch area). Some batsmen wear additional padding inside their shirts and trousers such as thigh pads, arm pads, rib protectors and shoulder pads. The only fielders allowed to wear protective gear are those in positions very close to the batsman (i.e., if they are alongside or in front of him), but they cannot wear gloves or external leg guards.
There are various formats ranging from Twenty20, played over a few hours with each team batting for a single innings of 20 overs, to Test matches, played over five days with unlimited overs and the teams each batting for two innings of unlimited length. Traditionally cricketers play in all-white kit, but in limited overs cricket they wear club or team colours. In addition to the basic kit, some players wear protective gear to prevent injury caused by the ball, which is a hard, solid spheroid made of compressed leather with a slightly raised sewn seam enclosing a cork core which is layered with tightly wound string.
Gryllus firmus exhibits wing polymorphism; some individuals have fully functional, long hind wings and others have short wings and cannot fly. The short-winged females have smaller flight muscles, greater ovarian development, and produce more eggs, so the polymorphism adapts the cricket for either dispersal or reproduction. In some long-winged individuals, the flight muscles deteriorate during adulthood and the insect's reproductive capabilities improve.
Cricket entered a new era in 1963 when English counties introduced the limited overs variant. As it was sure to produce a result, limited overs cricket was lucrative and the number of matches increased. The first Limited Overs International was played in 1971 and the governing International Cricket Council (ICC), seeing its potential, staged the first limited overs Cricket World Cup in 1975. In the 21st century, a new limited overs form, Twenty20, made an immediate impact. On 22 June 2017, Afghanistan and Ireland became the 11th and 12th ICC full members, enabling them to play Test cricket.
Crickets have a cosmopolitan distribution, being found in all parts of the world with the exception of cold regions at latitudes higher than about 55° North and South. They have colonised many large and small islands, sometimes flying over the sea to reach these locations, or perhaps conveyed on floating timber or by human activity. The greatest diversity occurs in tropical locations, such as in Malaysia, where 88 species were heard chirping from a single location near Kuala Lumpur. A greater number than this could have been present because some species are mute.
If a fielder is injured or becomes ill during a match, a substitute is allowed to field instead of him, but the substitute cannot bowl or act as a captain. The substitute leaves the field when the injured player is fit to return. The Laws of Cricket were updated in 2017 to allow substitutes to act as wicket-keepers, a situation that first occurred when Mumbai Indians' wicket-keeper Ishan Kishan was injured in a match on 18 April 2018.