yeast
yeast
UK[jiːst]US[jiːst]
n
A type of fungus used in making alcoholic drinks such as beer and wine, and for making bread swell and become light.
Etymology
The word 'yeast' originates from the Old English 'gist' or 'giest', meaning 'foam' or 'ferment'. This term is rooted in the Proto-Germanic 'jestuz', which is derived from the Proto-Indo-European root 'yes-', meaning 'to boil', 'foam', or 'ferment'. The semantic journey is direct and vivid: from the ancient concept of boiling and frothing to the specific modern agent of fermentation that causes dough to rise and liquids to bubble. Its spelling and pronunciation evolved through Middle English 'yeest', influenced by its verb form 'yeasen' (to ferment), solidifying the link between the substance and its frothy, active nature.
Analysis
The word 'yeast' is a simplex word of Germanic origin. It does not contain separable, meaningful morphemes within its modern English spelling.
Examples
The baker added fresh yeast to the dough to help it rise.
Yeast is essential for the fermentation process in brewing beer.
Nutritional yeast is often used as a cheese substitute in vegan cooking.