The game on the field is regulated by the two umpires, one of whom stands behind the wicket at the bowler's end, the other in a position called "square leg" which is about 15–20 metres away from the batsman on strike and in line with the popping crease on which he is taking guard. The umpires have several responsibilities including adjudication on whether a ball has been correctly bowled (i.e., not a no-ball or a wide); when a run is scored; whether a batsman is out (the fielding side must first appeal to the umpire, usually with the phrase "How's that?" or "Owzat?"); when intervals start and end; and the suitability of the pitch, field and weather for playing the game. The umpires are authorised to interrupt or even abandon a match due to circumstances likely to endanger the players, such as a damp pitch or deterioration of the light.
Crickets are kept as pets and are considered good luck in some countries; in China, they are sometimes kept in cages or in hollowed-out gourds specially created in novel shapes. The practice was common in Japan for thousands of years; it peaked in the 19th century, though crickets are still sold at pet shops. It is also common to have them as caged pets in some European countries, particularly in the Iberian Peninsula. Cricket fighting is a traditional Chinese pastime that dates back to the Tang dynasty (618–907). Originally an indulgence of emperors, cricket fighting later became popular among commoners. The dominance and fighting ability of males does not depend on strength alone; it has been found that they become more aggressive after certain pre-fight experiences such as isolation, or when defending a refuge. Crickets forced to fly for a short while will afterwards fight for two to three times longer than they otherwise would.
Crickets are hemimetabolic insects, whose lifecycle consists of an egg stage, a larval or nymph stage that increasingly resembles the adult form as the nymph grows, and an adult stage. The egg hatches into a nymph about the size of a fruit fly. This passes through about 10 larval stages, and with each successive moult, it becomes more like an adult. After the final moult, the genitalia and wings are fully developed, but a period of maturation is needed before the cricket is ready to breed.
Additional runs can be gained by the batting team as extras (called "sundries" in Australia) due to errors made by the fielding side. This is achieved in four ways: no-ball, a penalty of one extra conceded by the bowler if he breaks the rules; wide, a penalty of one extra conceded by the bowler if he bowls so that the ball is out of the batsman's reach; bye, an extra awarded if the batsman misses the ball and it goes past the wicket-keeper and gives the batsmen time to run in the conventional way; leg bye, as for a bye except that the ball has hit the batsman's body, though not his bat. If the bowler has conceded a no-ball or a wide, his team incurs an additional penalty because that ball (i.e., delivery) has to be bowled again and hence the batting side has the opportunity to score more runs from this extra ball.
One possible source for the sport's name is the Old English word "cryce" (or "cricc") meaning a crutch or staff. In Samuel Johnson's Dictionary, he derived cricket from "cryce, Saxon, a stick". In Old French, the word "criquet" seems to have meant a kind of club or stick. Given the strong medieval trade connections between south-east England and the County of Flanders when the latter belonged to the Duchy of Burgundy, the name may have been derived from the Middle Dutch (in use in Flanders at the time) "krick"(-e), meaning a stick (crook). Another possible source is the Middle Dutch word "krickstoel", meaning a long low stool used for kneeling in church and which resembled the long low wicket with two stumps used in early cricket. According to Heiner Gillmeister, a European language expert of Bonn University, "cricket" derives from the Middle Dutch phrase for hockey, met de (krik ket)sen (i.e., "with the stick chase"). Gillmeister has suggested that not only the name but also the sport itself may be of Flemish origin.
The Laws state that, throughout an innings, "the ball shall be bowled from each end alternately in overs of 6 balls". The name "over" came about because the umpire calls "Over!" when six balls have been bowled. At this point, another bowler is deployed at the other end, and the fielding side changes ends while the batsmen do not. A bowler cannot bowl two successive overs, although a bowler can (and usually does) bowl alternate overs, from the same end, for several overs which are termed a "spell". The batsmen do not change ends at the end of the over, and so the one who was non-striker is now the striker and vice-versa. The umpires also change positions so that the one who was at "square leg" now stands behind the wicket at the non-striker's end and vice-versa.
In 1876–77, an England team took part in what was retrospectively recognised as the first-ever Test match at the Melbourne Cricket Ground against Australia. The rivalry between England and Australia gave birth to The Ashes in 1882, and this has remained Test cricket's most famous contest. Test cricket began to expand in 1888–89 when South Africa played England.
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.