4.10
(a) A regulation game consists of nine innings, unless extended because of a tie score, or shortened (1) because the home team needs none of its half of the ninth inning or only a fraction of it, or (2) because the umpire calls the game. EXCEPTION: National Association leagues may adopt a rule providing that one or both games of a doubleheader shall be seven innings in length. In such games, any of these rules applying to the ninth inning shall apply to the seventh inning.
(b) If the score is tied after nine completed innings play shall continue until (1) the visiting team has scored more total runs than the home team at the end of a completed inning, or (2) the home team scores the winning run in an uncompleted inning.
(c) If a game is called, it is a regulation game:
(1) If five innings have been completed;
(2) If the home team has scored more runs in four or four and a fraction half-innings than the visiting team has scored in five completed half-innings;
(3) If the home team scores one or more runs in its half of the fifth inning to tie the score.
(d) If a regulation game is called with the score tied, it shall become a suspended game. See Rule 4.12.
(e) If a game is called before it has become a regulation game, the umpire shall declare it “No Game.”
(f) Rain checks will not be honored for any regulation or suspended game which has progressed to or beyond a point of play described in 4.10(c)

(a) A game shall become a suspended game that must be completed at a future date if the game is terminated for any of the following reasons:
(1) A curfew imposed by law;
(2) A time limit permissible under league rules;
(3) Light failure or malfunction of a mechanical field device under control of the home club. (Mechanical field device shall include automatic tarpaulin or water removal equipment);
(4) Darkness, when a law prevents the lights from being turned on;
(5) Weather, if a regulation game is called while an inning is in progress and before the inning is completed, and the visiting team has scored one or more runs to take the lead, and the home team has not retaken the lead; or
(6) It is a regulation game that is called with the score tied. National Association Leagues may also adopt the following rules for suspended games. (If adopted by a National Association League, Rule 4.10(e) would not apply to their games.):
(7) The game has not become a regulation game (41/2 innings with the home team ahead, or 5 innings with the visiting club ahead or tied).
(8) If a game is suspended before it becomes a regulation game, and is continued prior to another regularly scheduled game, the regularly scheduled game with be limited to seven innings.
(9) If a game is suspended after it is a regulation game, and is continued prior to another regularly scheduled game, the regularly scheduled game will be a nine inning game.
EXCEPTION: Optional Rules 4.12(a)(7), 4.12(a)(8) and 4.12(a)(9) for National Association Leagues will not apply to the last scheduled game between the two teams during the championship season or league playoffs.
No game called because of a curfew (Rule 4.12(a)(1)), weather (Rule 4.12(a)(5)), a time limit (Rule 4.12(a)(2)) or with a tied score (Rule 4.12(a)(6)) shall be a suspended game unless it has progressed far enough to have been a regulation game pursuant to Rule 4.10(c). A game called pursuant to Rules 4.12(a)(3) or 4.12(a)(4) shall be a suspended game at any time after it starts.
NOTE: Weather and similar conditions—Rules 4.12(a)(1) through 4.12(a)(5)—shall take precedence in determining whether a called game shall be a suspended game. If a game is halted by weather, and subsequent light failure or an intervening curfew or time limit prevents its resumption, the game shall not be a suspended game. If a game is halted by light failure, and weather or field conditions prevent its resumption, the game shall not be a suspended game. A game can only be considered a suspended game if stopped for any of the six reasons specified in Rule 4.12(a).
(b) A suspended game shall be resumed and completed as follows:
(1) Immediately preceding the next scheduled single game between the two clubs on the same grounds; or
(2) Immediately preceding the next scheduled doubleheader between the two clubs on the same grounds, if no single game remains on the schedule; or
(3) If suspended on the last scheduled date between the two clubs in that city, transferred and played on the grounds of the opposing club, if possible;
(i) Immediately preceding the next scheduled single game, or
(ii) Immediately preceding the next scheduled doubleheader, if no single game remains on the schedule.
(4) Any suspended game not completed prior to the last scheduled game between the two teams during the championship season shall become a called game. If such game becomes a called game and
(i) has progressed far enough to become a regulation game, and one team is ahead, the team that is ahead shall be declared the winner;
(ii) has progressed far enough to become a regulation game, and the score is tied, the game shall be declared a “tie game.” A tie game is to be replayed in its entirety, unless the league president determines that playing the rescheduled game is not necessary to affect the league championship; or
(iii)has not progressed far enough to become a regulation game, the game shall be declared “No Game.” In such case, the game is to be replayed in its entirety, unless the league president determines that playing the rescheduled game is not necessary to affect the league championship.
(c) A suspended game shall be resumed at the exact point of suspension of the original game. The completion of a suspended game is a continuation of the original game. The lineup and batting order of both teams shall be exactly the same as the lineup and batting order at the moment of suspension, subject to the rules governing substitution. Any player may be replaced by a player who had not been in the game prior to the suspension. No player removed before the suspension may be returned to the lineup.
A player who was not with the club when the game was suspended may be used as a substitute, even if he has taken the place of a player no longer with the club who would not have been eligible because he had been removed from the lineup before the game was suspended.
Rule 4.12(c) Comment: If immediately prior to the call of a suspended game, a substitute pitcher has been announced but has not retired the side or pitched until the batter becomes a baserunner, such pitcher, when the suspended game is later resumed may, but is not required to start the resumed portion of the game. However, if he does not start he will be considered as having been substituted for and may not be used in that game.
(d) Rain checks will not be honored for any regulation or suspended game that has progressed to or beyond a point of play described in Rule 4.10(c).