# yeast

/ˈjist/ (US) · /jˈiːst/ (UK)

Source: https://englishreference.com/word/yeast
Updated: 2026-06-20

## Senses

### 1. baking/brewing ingredient

noun · CEFR B2

a tiny fungus used to make bread rise or to make beer and wine.

For teachers: a unicellular fungus, specifically of the genus Saccharomyces, used as a leavening agent in baking and a fermenter in brewing.

- You need to mix the yeast with warm water and sugar before adding it to the flour.
- The baker monitored the temperature carefully, as excessive heat would kill the yeast and prevent the dough from rising properly.

Usage: Uncountable when referring to the substance generally; countable when referring to specific strains or packets.

### 2. biology

noun · CEFR C1 · Technical

a type of very small living thing that is a fungus.

For teachers: any of various small, single-celled fungi that reproduce by budding or fission.

- Scientists study how different types of yeast react to various sugars.
- The researcher isolated a specific strain of yeast from the skin of the grapes to study its unique fermentation properties.

### 3. to ferment

verb · CEFR C2 · Technical · Archaic

to bubble and change chemically, like when making beer.

For teachers: to undergo or cause fermentation; to become frothy through the action of fungi.

- The mixture began to yeast as the natural sugars broke down.
- The liquid was left in the vat to yeast for several days until the desired alcohol content was achieved.

### 4. to exaggerate

verb · CEFR C1 · Slang · Informal

to make a story seem bigger or more important than it really is.

For teachers: to inflate the truth or provide an exaggerated account of an event.

- He is always yeasting about how much money he makes at his new job.
- Don't listen to his version of the story; he tends to yeast whenever he wants to impress a new audience.

Teaching tip: This slang usage is relatively niche and often found in specific regional dialects; learners should use it cautiously.

## Examples

- The baker adds yeast to the dough to make it rise.
- If the water is too hot, it will kill the yeast and the bread will not expand.
- Modern industrial brewing relies on specific strains of yeast to ensure consistent flavor profiles and predictable fermentation times across different batches of beer.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.