Ninth

Part of speech: noun (n.)

1. The quotient of one divided by nine; one of nine equal parts of a thing; the next after the eighth.

2. An interval containing an octave and a second.

3. A chord of the dominant seventh with the ninth added.

Part of speech: adjective (a.)

1. Following the eight and preceding the tenth; coming after eight others.

2. Constituting or being one of nine equal parts into which anything is divided.