Ninth means the position that comes after eighth in a sequence, or one of nine equal parts of something.

When you're ninth in line for lunch, eight people stand ahead of you. If you finish ninth in a race, you crossed the finish line after eight other runners. The ninth inning is usually the last inning in a standard baseball game, when teams get their final chance to score.

The word also describes dividing something into nine pieces and taking one. If you eat a ninth of a pizza, you've eaten one slice from a pizza cut into nine equal parts. A ninth-grader is in their ninth year of formal schooling.

In music, a ninth is an interval that spans nine letter names on the scale, like from C up to the next D. Musicians sometimes add ninths to chords to create a rich sound in jazz and other styles.