How is a "sacrifice fly" defined?

A "sacrifice fly" is defined as a fly ball that is caught in the air, allowing a runner on base to advance and score. This play typically occurs with less than two outs, where the batter intentionally hits a fly ball to enable a teammate to tag up and score from third base. The key components of this definition include the fly ball's nature, the action of the runner tagging up, and the overall strategy of helping the team score while sacrificing the out.

In contrast, the other options do not accurately represent what constitutes a sacrifice fly. For instance, a pop-up caught by the infield does not allow a runner to score in the same strategic manner, nor does a bunted ball contribute to the same type of scoring opportunity associated with a sacrifice fly. Additionally, a ground ball hit with less than two outs does not involve the same mechanics as a sacrifice fly, as it does not typically lead to runners advancing in the same way.