Ninth (?), a. [From Nine; cf. AS. nigo&edh;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.
© Webster 1913.
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.
© Webster 1913.