tread vs stair

tread and stair both are nouns.

Word	Noun	Adjective	Verb	Adverb
tread	Yes	No	Yes	No
stair	Yes	No	No	No

tread (noun)	stair (noun)
a step in walking or running	support consisting of a place to rest the foot while ascending or descending a stairway
structural member consisting of the horizontal part of a stair or step
the part (as of a wheel or shoe) that makes contact with the ground
the grooved surface of a pneumatic tire

tread (verb)	stair (verb)
crush as if by treading on
brace (an archer's bow) by pressing the foot against the center
mate with (used of male birds)
tread or stomp heavily or roughly
put down or press the foot, place the foot
apply (the tread) to a tire