fatigue crack vs crevice

fatigue crack and crevice both are nouns.

Word	Noun	Adjective	Verb	Adverb
fatigue crack	Yes	No	No	No
crevice	Yes	No	No	No

As nouns, crevice is a hypernym of fatigue crack; that is, crevice is a word with a broader meaning than fatigue crack:

Other hypernyms of fatigue crack include cleft, crack, fissure, scissure.

fatigue crack (noun)	crevice (noun)
a crack in metal resulting from metal fatigue	a long narrow cleft
	a long narrow depression in a surface