whodunit vs mystery story

whodunit and mystery story both are nouns.

Word	Noun	Adjective	Verb	Adverb
whodunit	Yes	No	No	No
mystery story	Yes	No	No	No

As nouns, whodunit and mystery story are synonyms defined as:

whodunit and mystery story: a story about a crime (usually murder) presented as a novel or play or movie

Other synonyms of whodunit include mystery.

whodunit (noun)	mystery story (noun)
a story about a crime (usually murder) presented as a novel or play or movie	a story about a crime (usually murder) presented as a novel or play or movie