TB White

• He is declared out before reaching first base, or
• He reaches first base safely, or
• He hits a fair ball which causes a third out on another runner (see left on base)

An at bat (AB) is used to calculate certain statistics, including batting average, on-base percentage, and slugging percentage. It is a more restricted definition of a plate appearance.  A batter has an at bat every time he faces a pitcher, except in the following circumstances:

• He receives a base on balls (BB).
• He is hit by a pitch (HBP).
• He hits a sacrifice fly or a sacrifice hit (also known as sacrifice bunt).
• He is awarded first base due to interference or obstruction, usually by the catcher.
• The inning ends while he is still at bat (due to the third out being made by a runner caught stealing, for example). In this case, the batter will come to bat again in the next inning, though he now has no balls or strikes on him.