adjective

1. preceded by five others in a series; 6th
2. designating any of the six equal parts of something

Etymology: ME sixth < OE sixta, akin to Ger sechste, L sextus: see six & -th

noun

1. the one following the fifth
2. any of the six equal parts of something;
3. Music
   1. the sixth tone of an ascending diatonic scale, or a tone five degrees above or below any given tone in such a scale; submediant; superdominant
   2. the interval between two such tones, or a combination of them
   3. the chord formed by a triad in which the fundamental tone is raised an octave, creating a new interval of a sixth, as E-G-C
      in full sixth chord

adverb