Yeast

Part of speech: noun

Pronunciation: /jiːst/

Definitions

1. A single-celled fungus used in baking and brewing that ferments sugars to produce carbon dioxide and alcohol
2. A microorganism that belongs to the fungus kingdom and plays a crucial role in food production by fermenting sugars to generate carbon dioxide and alcohol
3. An essential fungus involved in the fermentation process in baking and beverage making, converting sugars into carbon dioxide and alcohol

Etymology: Yeast is one of the few English words whose ancestor meant something close to "foam" or "froth," and the link is still visible in German. The Old English form "ġist" was cognate with German "Gischt," meaning sea spray or foam, which makes sense for a substance that bubbles up as it ferments. Baking and brewing both depended on that bubbling, so the name followed the action rather than the organism, which no one could see at the time. The word has deep Germanic roots, reconstructed as "jestu" in Proto-Germanic. Its relatives are spread across the family: Dutch "gist," Swedish "jäst," Norwegian "jest," and Icelandic "jöstur" all mean the same thing, showing that the word was already well established across northern Europe long before English recorded it.

Synonyms: ferment, INVALID