ninth

adjective

1. preceded by eight others in a series; 9th
2. designating any of the nine equal parts of something

noun

1. the one following the eighth
2. any of the nine equal parts of something;
3. Music
   1. an interval in pitch of an octave and a second
   2. a tone separated from another by such an interval
   3. the combination of two such tones

adverb