one-fourth vs fourth part

one-fourth and fourth part both are nouns.

Word	Noun	Adjective	Verb	Adverb
one-fourth	Yes	No	No	No
fourth part	Yes	No	No	No

As nouns, one-fourth and fourth part are synonyms defined as:

Other synonyms of one-fourth include fourth, one-quarter, quarter, quartern, twenty-five percent.

one-fourth (noun)	fourth part (noun)
one of four equal parts	one of four equal parts