corbel step vs stair

corbel step and stair both are nouns.

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

As nouns, stair is a hypernym of corbel step; that is, stair is a word with a broader meaning than corbel step:

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

Other hypernyms of corbel step include step.

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