Crickets chirp at different rates depending on their species and the temperature of their environment. Most species chirp at higher rates the higher the temperature is (about 62 chirps a minute at 13 °C (55 °F) in one common species; each species has its own rate). The relationship between temperature and the rate of chirping is known as Dolbear's law. According to this law, counting the number of chirps produced in 14 seconds by the snowy tree cricket, common in the United States, and adding 40 will approximate the temperature in degrees Fahrenheit.
Off the field in televised matches, there is usually a third umpire who can make decisions on certain incidents with the aid of video evidence. The third umpire is mandatory under the playing conditions for Test and Limited Overs International matches played between two ICC full member countries. These matches also have a match referee whose job is to ensure that play is within the Laws and the spirit of the game.
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.
While the umpire (1) in shot stands at the bowler's end of the pitch, his colleague stands in the outfield, usually in or near the fielding position called "square leg", so that he is in line with the popping crease (7) at the striker's end of the pitch. The bowling crease (not numbered) is the one on which the wicket is located between the return creases (12). The bowler (4) intends to hit the wicket (9) with the ball (5) or, at least, to prevent the striker (8) from scoring runs. The striker (8) intends, by using his bat, to defend his wicket and, if possible, to hit the ball away from the pitch in order to score runs.
The main objective of each team is to score more runs than their opponents but, in some forms of cricket, it is also necessary to dismiss all of the opposition batsmen in their final innings in order to win the match, which would otherwise be drawn. If the team batting last is all out having scored fewer runs than their opponents, they are said to have "lost by n runs" (where n is the difference between the aggregate number of runs scored by the teams). If the team that bats last scores enough runs to win, it is said to have "won by n wickets", where n is the number of wickets left to fall. For example, a team that passes its opponents' total having lost six wickets (i.e., six of their batsmen have been dismissed) have won the match "by four wickets".