Main Entry:

¹yeast

Pronunciation:

\ˈyēst, especially Southern & Midland ˈēst\

Function:

noun

Etymology:

Middle English yest, from Old English gist; akin to Old High German jesen, gesen to ferment, Greek zein to boil

Date:

before 12th century

1 a: a yellowish surface froth or sediment that occurs especially in saccharine liquids (as fruit juices) in which it promotes alcoholic fermentation, consists largely of cells of a fungus (as the saccharomyces, Saccharomyces cerevisiae), and is used especially in the making of alcoholic liquors and as a leaven in baking b: a commercial product containing yeast fungi in a moist or dry medium c (1): a unicellular fungus that is present and functionally active in yeast, usually has little or no mycelium, and reproduces by budding (2): any of various similar fungi2archaic : the foam or spume of waves3: something that causes ferment or activity <were all seething with the yeast of revolt — J. F. Dobie>