- yeast, barm - a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey
--1 is a kind of leaven, leavening
--1 has particulars: yeast cake; brewer's yeast; mother - yeast - any of various single-celled fungi that reproduce asexually by budding or division
--2 is a kind of fungus
--2 is a member of Endomycetales, order Endomycetales
--2 has particulars:baker's yeast, brewer's yeast, Saccharomyces cerevisiae; wine-maker's yeast, Saccharomyces ellipsoides