stair vs corbie-step

stair and corbie-step both are nouns.

Word	Noun	Adjective	Verb	Adverb
stair	Yes	No	No	No
corbie-step	Yes	No	No	No

As nouns, corbie-step is a hyponym of stair; that is, corbie-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
corbie-step: (architecture) a step on the top of a gable wall

Other hyponyms of stair include corbel step, corbiestep, crow step.

stair (noun)	corbie-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