In the sport of cricket, a declaration occurs when a captain declares his team's innings closed and a forfeiture occurs when a captain chooses to forfeit an innings. Declaration and forfeiture are covered in Law 15 of the laws of cricket. This concept applies only to matches in which each team is scheduled to bat in two innings; Law 15 specifically does not apply in any form of limited overs cricket.
The captain of the batting side may declare an innings closed, when the ball is dead, at any time during a match. Usually this is because the captain thinks his team has already scored enough runs to win the match, though tactical declarations are sometimes used in other circumstances.
A captain considering declaration must balance the risks of declaring too early (thus setting too low a target for the opposing team) against those of declaring too late or not at all (thus causing a draw by leaving insufficient time to complete the match).
The first captain to declare was Charles Wright in 1890. In a game against Kent at the Bat and Ball Ground in Gravesend, Wright declared Nottinghamshire's second innings closed on 157 for 5 to set Kent a target of 231 to win. However, the tactic did not come off as the game was drawn with Kent on 98 for 9 and Nottinghamshire requiring one more wicket to win.
Before declarations were made legal, batsmen of a team that wanted to get the other team to bat again would deliberately get themselves out, leading to some farcical situations, where the fielding side would make no attempt to dismiss a batsman who was trying to be dismissed.
Under the current Laws, a captain may forfeit either of his side's innings. A forfeited innings shall be considered as a completed innings. Usually this happens in shorter competitive two-innings matches, where captains need to agree with each other how to set up the match so that there is a reasonable chance of a result. Winning a game gains a team considerably more points than drawing it, so captains are often willing to risk giving the opposition an opportunity to win that they otherwise would not have had as long as they are getting a similar opportunity in return.