adjective
The ordinal form of the number five.
noun
(ellipsis or nominalization) The person or thing in the fifth position.
One of five equal parts of a whole: one-fifth.
(US) A quantity of liquor equal to one-fifth of an American gallon, or, more commonly, 750 milliliters (that is, three quarters of a liter).
(music) The musical interval between one note and another five scale degrees higher (the fifth note in a scale)
The fifth voice in a polyphonic melody.
verb
(music) To sing in the fifth voice in a polyphonic melody.
(transitive, informal) To support something fifth, after four others have already done so.
(transitive, nonstandard) To divide by five.