stairs vs ladder

stairs and ladder both are nouns.

Word	Noun	Adjective	Verb	Adverb
stairs	Yes	No	No	No
ladder	Yes	No	Yes	No

As nouns, ladder is a hyponym of stairs; that is, ladder is a word with a more specific, narrower meaning than stairs:

stairs: a flight of stairs or a flight of steps
ladder: steps consisting of two parallel members connected by rungs; for climbing up or down

stairs (noun)	ladder (noun)
a flight of stairs or a flight of steps	steps consisting of two parallel members connected by rungs; for climbing up or down
	a row of unravelled stitches
	ascending stages by which somebody or something can progress

stairs (verb)	ladder (verb)
	come unraveled or undone as if by snagging