twenty percent vs fifth

twenty percent and fifth both are nouns.

Word	Noun	Adjective	Verb	Adverb
twenty percent	Yes	No	No	No
fifth	Yes	Yes	No	No

As nouns, twenty percent and fifth are synonyms defined as:

Other synonyms of twenty percent include fifth part, one-fifth.

twenty percent (noun)	fifth (noun)
one part in five equal parts	the musical interval between one note and another five notes away from it
	one part in five equal parts
	a quantity of liquor equal to one fifth of a United States gallon
	position five in a countable series of things

twenty percent (adjective)	fifth (adjective)
	coming next after the fourth and just before the sixth in position