Definition of: fifth

(fifth) adjective
1. Next in order after the fourth: the ordinal of five.
2. Being one of five equal parts: a fifth part.
—noun
1. One of five equal parts of anything.
2. The quotient of a unit divided by five.
3. Music a The interval between any note and the fifth note above it in the diatonic scale, counting the starting point as one (see SCALE²). b A note separated by this interval from any other, considered in relation to that other; specifically, the fifth above the keynote; the dominant.
4. One fifth of a U.S. gallon used as a measure of spirituous liquors.
—adverb In the fifth order, place, or rank: also, in formal discourse, fifth′ly.