Single wicket was popular in the 18th and 19th centuries and its matches were generally considered top-class. In this form, although each team may have from one to six players, there is only one batsman in at a time and he must face every delivery bowled while his innings lasts. Single wicket has rarely been played since limited overs cricket began. Matches tended to have two innings per team like a full first-class one and they could end in a draw.
The wicket-keeper (sometimes called simply the "keeper") is a specialist fielder subject to various rules within the Laws about his equipment and demeanour. He is the only member of the fielding side who can effect a stumping and is the only one permitted to wear gloves and external leg guards. Depending on their primary skills, the other ten players in the team tend to be classified as specialist batsmen or specialist bowlers. Generally, a team will include five or six specialist batsmen and four or five specialist bowlers, plus the wicket-keeper.
Cricket is a multi-faceted sport with multiple formats that can effectively be divided into first-class cricket, limited overs cricket and, historically, single wicket cricket. The highest standard is Test cricket (always written with a capital "T") which is in effect the international version of first-class cricket and is restricted to teams representing the twelve countries that are full members of the ICC (see above). Although the term "Test match" was not coined until much later, Test cricket is deemed to have begun with two matches between Australia and England in the 1876–77 Australian season; since 1882, most Test series between England and Australia have been played for a trophy known as The Ashes. The term "first-class", in general usage, is applied to top-level domestic cricket. Test matches are played over five days and first-class over three to four days; in all of these matches, the teams are allotted two innings each and the draw is a valid result.
In 1975, Dr. William H. Cade discovered that the parasitic tachinid fly Ormia ochracea is attracted to the song of the cricket, and uses it to locate the male to deposit her larvae on him. It was the first known example of a natural enemy that locates its host or prey using the mating signal. Since then, many species of crickets have been found to be carrying the same parasitic fly, or related species. In response to this selective pressure, a mutation leaving males unable to chirp was observed amongst a population of Teleogryllus oceanicus on the Hawaiian island of Kauai, enabling these crickets to elude their parasitoid predators. A different mutation with the same effect was also discovered on the neighboring island of Oahu (ca. 100 miles (160 km) away). Recently, new "purring" males of the same species in Hawaii are able to produce a novel auditory sexual signal that can be used to attract females while greatly reducing the likelihood of parasitoid attack from the fly.
Crickets have many natural enemies and are subject to various pathogens and parasites. They are eaten by large numbers of vertebrate and invertebrate predators and their hard parts are often found during the examination of animal intestines. Mediterranean house geckos (Hemidactylus turcicus) have learned that although a calling decorated cricket (Gryllodes supplicans) may be safely positioned in an out-of-reach burrow, female crickets attracted to the call can be intercepted and eaten.
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.
If the match has only a single innings per side, then a maximum number of overs applies to each innings. Such a match is called a "limited overs" or "one-day" match, and the side scoring more runs wins regardless of the number of wickets lost, so that a draw cannot occur. If this kind of match is temporarily interrupted by bad weather, then a complex mathematical formula, known as the Duckworth-Lewis method after its developers, is often used to recalculate a new target score. A one-day match can also be declared a "no-result" if fewer than a previously agreed number of overs have been bowled by either team, in circumstances that make normal resumption of play impossible; for example, wet weather.
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.