Ninth
In music, a ninth is a compound interval consisting of an octave plus a second.
Like the second, the interval of a ninth is classified as a dissonance in common practice tonality. Since a ninth is an octave larger than a second, its sonority level is considered less dense.
Wikipedia
Nineth (adjective)
alternative spelling of ninth
Ninth (adjective)
The ordinal form of the number nine.
Ninth (noun)
The person or thing in the ninth position.
Ninth (noun)
One of nine equal parts of a whole.
Wiktionary