The official definition depends based on NCAA, NPF, etc, but a good rule of thumb is divide the number of innings in the game by 2 and round up any fractional amount. So, in MLB, 9 becomes 4.5 rounded to 5 innings needed. Fastpitch is 7 becomes 3.5, rounded to 4. (If it is a sanctioned 5...
NFHS: 2.56.3 - The strike zone is the space over home plate which is between the batter's forward armpit and the top of the knees when the batter assumes a natural batting stance. Any part of the ball passing through the batter's strike zone in flight shall be considered a strike. The umpire...