fourth part vs fourth

fourth part and fourth both are nouns.

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

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

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

fourth part (noun)	fourth (noun)
one of four equal parts	the musical interval between one note and another four notes away from it
	one of four equal parts
	following the third position; number four in a countable series

fourth part (adjective)	fourth (adjective)
	coming next after the third and just before the fifth in position or time or degree or magnitude

fourth part (adverb)	fourth (adverb)
	in the fourth place