Ninth (?), a. [From Nine; cf.
AS. nigoða.] 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.
Ninth, n. 1. The
quotient of one divided by nine; one of nine equal parts of a thing;
the next after the eighth.
2. (Mus.) (a) An
interval containing an octave and a second. (b)
A chord of the dominant seventh with the ninth added.