(1):
(a.) Constituting or being one of nine equal parts into which anything is divided.
(2):
(n.) The quotient of one divided by nine; one of nine equal parts of a thing; the next after the eighth.
(3):
(a.) Following the eight and preceding the tenth; coming after eight others.
(4):
(n.) A chord of the dominant seventh with the ninth added.
(5):
(n.) An interval containing an octave and a second.