Ninth

Definition:

(a.) Following the eight and preceding the tenth; coming after eight others.
(a.) Constituting or being one of nine equal parts into which anything is divided.
(n.) The quotient of one divided by nine; one of nine equal parts of a thing; the next after the eighth.
(n.) An interval containing an octave and a second.
(n.) A chord of the dominant seventh with the ninth added.

Compare ninth with other words:

ninth vs. novennial