Crickets are small to medium-sized insects with mostly cylindrical, somewhat vertically flattened bodies. The head is spherical with long slender antennae arising from cone-shaped scapes (first segments) and just behind these are two large compound eyes. On the forehead are three ocelli (simple eyes). The pronotum (first thoracic segment) is trapezoidal in shape, robust, and well-sclerotinized. It is smooth and has neither dorsal or lateral keels (ridges).
A match's statistics are summarised on a scorecard. Prior to the popularisation of scorecards, most scoring was done by men sitting on vantage points cuttings notches on tally sticks and runs were originally called notches. According to Rowland Bowen, the earliest known scorecard templates were introduced in 1776 by T. Pratt of Sevenoaks and soon came into general use. It is believed that scorecards were printed and sold at Lord's for the first time in 1846.
At the tip of the abdomen is a pair of long cerci (paired appendages on rearmost segment), and in females, the ovipositor is cylindrical, long and narrow, smooth and shiny. The femora (third segments) of the back pair of legs are greatly enlarged for jumping. The tibiae (fourth segments) of the hind legs are armed with a number of moveable spurs, the arrangement of which is characteristic of each species. The tibiae of the front legs bear one or more tympani which are used for the reception of sound.
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.
As illustrated above, the pitch is marked at each end with four white painted lines: a bowling crease, a popping crease and two return creases. The three stumps are aligned centrally on the bowling crease, which is eight feet eight inches long. The popping crease is drawn four feet in front of the bowling crease and parallel to it; although it is drawn as a twelve-foot line (six feet either side of the wicket), it is, in fact, unlimited in length. The return creases are drawn at right angles to the popping crease so that they intersect the ends of the bowling crease; each return crease is drawn as an eight-foot line, so that it extends four feet behind the bowling crease, but is also, in fact, unlimited in length.
The decision to attempt a run is ideally made by the batsman who has the better view of the ball's progress, and this is communicated by calling: usually "yes", "no" or "wait". More than one run can be scored from a single hit: hits worth one to three runs are common, but the size of the field is such that it is usually difficult to run four or more. To compensate for this, hits that reach the boundary of the field are automatically awarded four runs if the ball touches the ground en route to the boundary or six runs if the ball clears the boundary without touching the ground within the boundary. In these cases the batsmen do not need to run. Hits for five are unusual and generally rely on the help of "overthrows" by a fielder returning the ball. If an odd number of runs is scored by the striker, the two batsmen have changed ends, and the one who was non-striker is now the striker. Only the striker can score individual runs, but all runs are added to the team's total.
Crickets are found in many habitats. Members of several subfamilies are found in the upper tree canopy, in bushes, and among grasses and herbs. They also occur on the ground and in caves, and some are subterranean, excavating shallow or deep burrows. Some make home in rotting wood, and certain beach-dwelling species can run and jump over the surface of water.
Most crickets lay their eggs in the soil or inside the stems of plants, and to do this, female crickets have a long, needle-like or sabre-like egg-laying organ called an ovipositor. Some ground-dwelling species have dispensed with this, either depositing their eggs in an underground chamber or pushing them into the wall of a burrow. The short-tailed cricket (Anurogryllus) excavates a burrow with chambers and a defecating area, lays its eggs in a pile on a chamber floor, and after the eggs have hatched, feeds the juveniles for about a month.
Some species, such as Gryllus assimilis, take off, fly, and land efficiently and well, while other species are clumsy fliers. In some species, the hind wings are shed, leaving wing stumps, usually after dispersal of the insect by flight. In other species, they may be pulled off and consumed by the cricket itself or by another individual, probably providing a nutritional boost.
The folklore and mythology surrounding crickets is extensive. The singing of crickets in the folklore of Brazil and elsewhere is sometimes taken to be a sign of impending rain, or of a financial windfall. In Álvar Núñez Cabeza de Vaca's chronicles of the Spanish conquest of the Americas, the sudden chirping of a cricket heralded the sighting of land for his crew, just as their water supply had run out. In Caraguatatuba, Brazil, a black cricket in a room is said to portend illness; a gray one, money; and a green one, hope. In Alagoas state, northeast Brazil, a cricket announces death, thus it is killed if it chirps in a house. In Barbados, a loud cricket means money is coming in; hence, a cricket must not be killed or evicted if it chirps inside a house. However, another type of cricket that is less noisy forebodes illness or death.
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 ICC also organises competitions that are for several countries at once, including the Cricket World Cup, ICC T20 World Cup and ICC Champions Trophy. A league competition for Test matches played as part of normal tours, the ICC World Test Championship, had been proposed several times, and its first instance began in 2019. A league competition for ODIs, the 2020–22 ICC Cricket World Cup Super League, is planned to begin in 2020. The ICC maintains Test rankings, ODI rankings and T20 rankings systems for the countries which play these forms of cricket.
At the grassroots level, local club cricket is essentially an amateur pastime for those involved but still usually involves teams playing in competitions at weekends or in the evening. Schools cricket, first known in southern England in the 17th century, has a similar scenario and both are widely played in the countries where cricket is popular. Although there can be variations in game format, compared with professional cricket, the Laws are always observed and club/school matches are therefore formal and competitive events. The sport has numerous informal variants such as French cricket.