riser vs riser main

riser and riser main both are nouns.

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

As nouns, riser and riser main are synonyms defined as:

Other synonyms of riser include riser pipe, riser pipeline.

riser (noun)	riser main (noun)
structural member consisting of the vertical part of a stair or step	a vertical pipe in a building
a vertical pipe in a building
a person who rises (especially from bed)