drywall vs gypsum board

drywall and gypsum board both are nouns.

Word	Noun	Adjective	Verb	Adverb
drywall	Yes	No	No	No
gypsum board	Yes	No	No	No

As nouns, gypsum board is a hyponym of drywall; that is, gypsum board is a word with a more specific, narrower meaning than drywall:

drywall: a wide flat board used to cover walls or partitions; made from plaster or wood pulp or other materials and used primarily to form the interior walls of houses
gypsum board: wallboard with a gypsum plaster core bonded to layers of paper or fiberboard; used instead of plaster or wallboard to make interior walls

Other hyponyms of drywall include beaver board, fiberboard, fibreboard, particle board, plasterboard.

drywall (noun)	gypsum board (noun)
a wide flat board used to cover walls or partitions; made from plaster or wood pulp or other materials and used primarily to form the interior walls of houses	wallboard with a gypsum plaster core bonded to layers of paper or fiberboard; used instead of plaster or wallboard to make interior walls