barm vs yeast cake

barm and yeast cake both are nouns.

Word	Noun	Adjective	Verb	Adverb
barm	Yes	No	No	No
yeast cake	Yes	No	No	No

As nouns, yeast cake is a hyponym of barm; that is, yeast cake is a word with a more specific, narrower meaning than barm:

barm: a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey
yeast cake: small cake of compressed moist yeast

Other hyponyms of barm include brewer's yeast, mother.

barm (noun)	yeast cake (noun)
a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey	small cake of compressed moist yeast