In baseball, a force is a situation when a baserunner is compelled (or forced) to vacate his time-of-pitch base--and thus try to advance to the next base--because the batter became a runner. A runner at first base is always forced to attempt to advance to second base when the batter becomes a runner. Runners at second or third base are forced only when all bases preceding their time-of-pitch base are occupied by other baserunners and the batter becomes a runner.
A forced runner's force base is the next base beyond his time-of-pitch base. Any attempt by fielders to put a forced runner out is called a force play. A forced runner is out (called a force out) when a fielder with the ball touches the runner's force base before the runner reaches that base. A forced runner also may be tagged out in the usual fashion as well; such a tag is still considered a force play if the tag is made before the runner reaches his force base. Any play on the batter-runner before he reaches first base is the same as a force play, though the rules technically do not include this in the definition of a force play.
A force on a runner is "removed" when the batter or a following runner is put out. This most often happens on fly outs--on such, the batter-runner is out, and the other runner(s) usually return to their time-of-pitch base because they are no longer forced to advance.
Scoring on force outsEdit
No run can be scored during the same continuous playing action as a force out for the third out, even if a runner reaches home plate before the third out is recorded. As a result, on a batted ball with two outs, fielders will nearly always ignore a runner trying to score, attempting instead to force out the batter or another runner.
An appeal play may also be a force play; for example, with runners on first and third bases and two out, the batter gets a hit but the runner from first misses second base on the way to third. After a proper appeal, this runner will be called out. This is a force out because the runner was out for failing to touch a base to which he was forced; this force out is the third out and thus the run does not score. However, most appeals are not force plays, because appeals usually do not involve a forced runner.