Pronunciation: (nīnth),[key] —adj. 1. next after the eighth; being the ordinal number for nine.
2. being one of nine equal parts.
—n. 1. a ninth part, esp. of one (1/9).
2. the ninth member of a series.
3. Music. a. a tone distant from another tone by an interval of an octave and a second.
b. the interval between such tones.
c. harmonic combination of such tones.