For more examples, click here.

A Fly Ball Double

A batter advancing to second base on a base hit, no matter where the ball is hit, and provided there's no error on the play, is called a double. There are some other considerations here, but we'll get to them in a second.

For a ball in the air to go for a double, you’re almost always looking at a solidly-hit line drive that goes either into “the gap” (the space on either side of the center fielder where center field overlaps with left and right fields), or down one of the base lines, perhaps even landing fair and them bouncing into foul territory. You can also see balls in the air go for doubles on defensive misplays (that fall short of being errors); when the ball is hit into the air and there’s no one else on base, the batter doesn’t really need to stop at first; so if the defense is sub-optimal, said batter can just keep on running until they pull up safely at a base.

Any baserunners who are on when the batter hits a double will more than likely score, and most will be able to do so without a throw¹. If there was a runner on first, the defense might have a chance at getting that runner at the plate, but that’s about it. If the runner on first is slow, or if they get a bad read on the ball, think it’s going to be caught, and go back to tag up, they might wind up only being able to get to third base. That’s still not too bad. It’s better to have runners on second and third with [whatever amount of outs you had starting out] than a runner on second with [one more out than the previous hypothetical].

Just because a batter hits the ball and winds up on second, does not mean they are always credited with a double, as we hinted at the start of this section. An error is an obvious example— either the error will have allowed the batter to reach base when they wouldn't have, or to advance a base instead of staying at first. Either way, no double. Similarly, if a batter reaches first when there are other runners on base, and while the defense is preoccupied with those runners, the runner on first moves up to second, that doesn't count on a double. That's a single, with the advance coming on the defensive play. Usually this means the runner is going to second while the fielders are throwing the ball, so it's called an advance on the throw. On the flip side, if the batter/runner makes it to second safely, but tries to stretch to third, and gets thrown out in the process, they are still credited with a double.