An innings, or inning, is a segment of a game in any of a variety of sports – most notably baseball and cricket – during which a side takes its turn to bat. In cricket, the term innings is both singular and plural and is always spelled and pronounced with the terminal "s". In baseball, the singular form is inning and only the plural takes an "s".
In many other sports, the length of the game is dictated by a clock and teams swap offensive and defensive roles dynamically by taking possession of a ball or similar item. In cricket and baseball, however, one team known as the batting team attempts to score points (known as runs in both sports), while the other team, known as the fielding team, attempts to prevent the scoring of runs and get members of the batting team out. The teams switch places after the fielding team has succeeded in getting a fixed number of players out, making a clock unnecessary.
In cricket, the term innings is also used to refer to the play of one particular player (Smith had a poor innings, scoring only 12). By extension, this term can be used in British English for almost any activity which takes a period of time (The Liberal government had a good innings, but finally lost office in 1972, or You've had a fair innings, now it's my turn, meaning "you have spoken for long enough, now let me speak"). It is also used in reference to someone who has died at a reasonably old age (Ah, well. John was 83. At least he had a good innings.). The parallel to this in baseball is an at bat.
In First-class cricket and Test cricket, each side has two innings. In one-day cricket and other abbreviated forms of the game, an innings lasts only for a set period or for a certain number of overs (typically 50). Note that "an innings" can mean either a particular side's innings (Sri Lanka made 464 in the third innings (of the game)) or that of both sides (England had the better of the first innings, outscoring Australia by 104), the difference being understood by context.
An individual innings usually lasts until the batsman is given out, or until the end of the team innings. Although batsmen bat together in pairs, this combination is never called an innings: it is a partnership or a stand.
If the score is tied after 9 innings, the game goes into extra innings until an inning ends with one team ahead of the other. As in the case of the ninth inning, a home team which scores to take a lead in any extra inning automatically wins, and the inning is considered complete at that moment regardless of the number of outs.
In US English, this baseball-originated terminology is sometimes found in non-sports usage in a tense situation: "it's the bottom of the ninth with the home team behind," meaning "there isn't much time to turn things around here."