riser vs pipe

riser and pipe both are nouns.

Word	Noun	Adjective	Verb	Adverb
riser	Yes	No	No	No
pipe	Yes	No	Yes	No

As nouns, pipe is a hypernym of riser; that is, pipe is a word with a broader meaning than riser:

riser: a vertical pipe in a building
pipe: a long tube made of metal or plastic that is used to carry water or oil or gas etc.

Other hypernyms of riser include pipage, piping.

riser (noun)	pipe (noun)
structural member consisting of the vertical part of a stair or step	a long tube made of metal or plastic that is used to carry water or oil or gas etc.
a vertical pipe in a building	a tube with a small bowl at one end; used for smoking tobacco
a person who rises (especially from bed)	the flues and stops on a pipe organ
	a tubular wind instrument
	a hollow cylindrical shape