stair vs crow step

stair and crow step both are nouns.

Word	Noun	Adjective	Verb	Adverb
stair	Yes	No	No	No
crow step	Yes	No	No	No

As nouns, crow step is a hyponym of stair; that is, crow step is a word with a more specific, narrower meaning than stair:

stair: support consisting of a place to rest the foot while ascending or descending a stairway
crow step: (architecture) a step on the top of a gable wall

Other hyponyms of stair include corbel step, corbie-step, corbiestep.

stair (noun)	crow step (noun)
support consisting of a place to rest the foot while ascending or descending a stairway	(architecture) a step on the top of a gable wall