mystery story vs whodunit

mystery story and whodunit both are nouns.

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

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

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

Other synonyms of mystery story include mystery.

mystery story (noun)	whodunit (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