[ yeest ]
/ yist /
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See synonyms for: yeast / yeasted / yeasting on Thesaurus.com

verb (used without object)
to ferment.
to be covered with froth.
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Origin of yeast

before 1000; Middle English ye(e)st (noun), Old English gist, gyst; cognate with Dutch gist,German Gischt yeast, foam, Old Norse jastr yeast, Greek zestós boiled, Sanskrit yásati (it) boils


yeastless, adjectiveyeastlike, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use yeast in a sentence

British Dictionary definitions for yeast

/ (jiːst) /

any of various single-celled ascomycetous fungi of the genus Saccharomyces and related genera, which reproduce by budding and are able to ferment sugars: a rich source of vitamins of the B complex
any yeastlike fungus, esp of the genus Candida, which can cause thrush in areas infected with it
a commercial preparation containing yeast cells and inert material such as meal, used in raising dough for bread or for fermenting beer, whisky, etcSee also brewer's yeast
a preparation containing yeast cells, used to treat diseases caused by vitamin B deficiency
froth or foam, esp on beer
(intr) to froth or foam

Derived forms of yeast

yeastless, adjectiveyeastlike, adjective

Word Origin for yeast

Old English giest; related to Old Norse jostr, Old High German jesan, Swedish esa, Norwegian asa, Sanskrit yasati
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for yeast

[ yēst ]

Any of various one-celled fungi that reproduce by budding and can cause the fermentation of carbohydrates, producing carbon dioxide and ethanol. There are some 600 known species of yeast, though they do not form a natural phylogenic group. Most yeasts are ascomycetes, but there are also yeast species among the basidiomycetes and zygomycetes. The budding processes in yeasts show a wide range of variations. In many yeasts, for example, the buds break away as diploid cells. Other yeasts reproduce asexually only after meiosis, and their haploid buds act as gametes that can combine to form a diploid cell, which functions as an ascus and undergoes meiosis to produce haploid spores. Still other yeasts form buds in both haploid and diploid phases. The ascomycete yeast Saccharomyces cerevisiae is used in baking to produce the carbon dioxide that leavens dough and batter. It has been the subject of extensive research in cell biology, and its genome was the first to be sequenced among eukaryotes. A variety of yeasts of the genus Saccharomyces are used in making beer and wine to provide alcohol content and flavor. Certain other yeasts, such as Candida albicans, are pathogenic in humans.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.