brewer's yeast vs barm

brewer's yeast and barm both are nouns.

Word	Noun	Adjective	Verb	Adverb
brewer's yeast	Yes	No	No	No
barm	Yes	No	No	No

As nouns, barm is a hypernym of brewer's yeast; that is, barm is a word with a broader meaning than brewer's yeast:

brewer's yeast: yeast used in fermenting beer
barm: a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey

Other hypernyms of brewer's yeast include yeast.

brewer's yeast (noun)	barm (noun)
used as a leaven in baking and brewing	a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey
yeast used in fermenting beer