yeast

yeast — noun

1. a type of microscopic fungus that people mix into bread dough so the dough expan

1.nounB1
Definition

a type of microscopic fungus that people mix into bread dough so the dough expands and becomes light; brewers and winemakers also add it to fruit or grain liquids so the natural sugar changes into alcohol.

Example

Romi added dried yeast to the warm milk and sugar before mixing in the flour.

dried yeast (common form)

The bread did not rise well because the yeast was too old to work.

yeast + rise / too old to work

Common collocations
  • dried yeast
  • fresh yeast
  • active dry yeast
  • instant yeast
  • brewer's yeast
  • yeast mixture
  • yeast dough
  • yeast extract
Synonyms
  • leaven

    more general term for any substance that makes dough rise; 'leaven' can also be used figuratively, while 'yeast' is mainly literal and concrete

  • starter

    a naturally fermented mixture of flour and water that contains wild yeast, used in sourdough bread; 'starter' is a specific product rather than a general type of fungus

Antonyms
  • baking powder

    a chemical leavening agent that works through acid-base reaction rather than living fungal activity; used when no fermentation flavour is wanted

Grammar Patterns

yeast + [verb]

dried/active/fresh + yeast

yeast + for + [purpose]

Usage Note

In everyday cooking, yeast usually refers to the dry or fresh product sold in packets or blocks. Active dry yeast and instant yeast are the two most common forms. All-purpose flour is often paired with yeast in standard bread recipes.

Common Mistakes

The yeast made the bread taste sweet.
The yeast made the bread rise and become fluffy.
Yeast causes rising through fermentation, not sweetness. Sugar may be added to feed the yeast, but the yeast itself does not make bread sweet.
I forgot to put yeast in the cake.
I forgot to put yeast in the bread.
Cakes usually use baking powder or baking soda as a leavening agent, not yeast.

2. a single-celled type of fungus that can multiply by splitting or forming buds, a

2.nounB2
Definition

a single-celled type of fungus that can multiply by splitting or forming buds, and that causes the chemical process in which sugar changes into alcohol.

Example

Under the microscope, Gabriel could see the round yeast cells splitting to form new ones.

yeast cells splitting (budding reproduction)

Biologists study yeast as a model because it grows fast and shares genes with people.

yeast as a model organism in research

Common collocations
  • yeast cell
  • yeast strain
  • yeast culture
  • yeast genome
  • yeast extract
  • budding yeast
  • yeast colony
Synonyms
  • fungus

    much broader category that includes mushrooms and moulds; 'yeast' is one specific type of fungus

  • Saccharomyces cerevisiae

    the scientific name of the most common baker's and brewer's yeast; far more technical than 'yeast'

  • microorganism

    even broader term covering all microscopic life forms (bacteria, protozoa, etc.), not specific to yeast

Grammar Patterns

yeast + cell / strain / culture

yeast + reproduces / grows / ferments

Usage Note

This sense is mainly used in biology and microbiology. 'Yeast' in this context is an uncountable noun referring to the whole group of organisms (Saccharomycetes). When referring to individual species, writers often use 'yeasts' as a countable plural.

Common Mistakes

Yeast is a kind of bacteria.
Yeast is a kind of fungus.
Yeast belongs to the fungus kingdom, not to bacteria. The two groups differ in cell structure, reproduction, and genetics.
Each yeast has one cell.
Each yeast cell is a single organism.
'Yeast' as an uncountable noun names the group; for individual organisms say 'yeast cell' or use the plural 'yeasts' when listing species.

yeast — verb

Word family

  • yeasty
    adjectiveC2
  • yeastless
    adjectiveC2

Synonym discussion

Sense: noun/1

All four of these words refer to substances that make dough rise, but they work in very different ways. 'Yeast' is a living fungus that produces carbon dioxide gas through fermentation, giving bread its characteristic flavour and texture. 'Leaven' is a broader, slightly old-fashioned term that can refer to any rising agent, including yeast, and is also used figuratively (e.g. 'the leaven of change'). 'Baking powder' and 'baking soda' are chemical leavening agents that produce gas through acid-base reactions rather than biological activity; they are used in cakes and quick breads where no fermentation time is needed. 'Starter' refers to a fermented mixture of flour and water containing wild yeast and bacteria, used specifically for sourdough bread. If you want a loaf with a rich, tangy flavour and airy crumb, you use yeast or a starter. If you are making pancakes or muffins, you reach for baking powder instead.

leavenbaking powderbaking sodastarter ↗

Common collocations

Nouns

  • yeast infection
  • yeast extract
  • yeast powder
  • yeast culture

Phrases

  • a pinch of yeast
  • packet of yeast
  • yeast-based [product]

Prepositions

  • yeast in [dough/liquid]
  • yeast for [baking/brewing]

Etymology

Proto-Indo-EuropeanProto-GermanicOld EnglishMiddle EnglishEnglish

The word 'yeast' comes from Old English 'gist' or 'giest', which developed from a Proto-Germanic root *jestuz, meaning 'foam' or 'froth'. This Germanic root goes back to the Proto-Indo-European *yes- ('to boil, foam, bubble'). The name reflects what people first noticed about yeast: when added to sugary liquids, it makes the mixture bubble and foam violently — visual evidence of fermentation. The word has kept this core connection to frothing and rising for over a thousand years.