leaven

From Middle English levain, borrowed from Old French, from Late Latin levāmen, instead of levāmentum, ultimately from Latin levō (“I raise”).

• (UK, US) IPA^(key): /ˈlɛv.ən/

• Audio (US)

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• Rhymes: -ɛvən

leaven (countable and uncountable, plural leavens)

1. Any agent used to make dough rise or to have a similar effect on baked goods.
2. (figuratively) Anything that makes a general assimilating change in the mass.
   • Bible, Luke xii. 1

     Beware of the leaven of the Pharisees, which is hypocrisy.

• leavenless
• natural leaven

leaven (third-person singular simple present leavens, present participle leavening, simple past and past participle leavened)

1. (transitive) To add a leavening agent.
2. (transitive) To cause to rise by fermentation.
3. (transitive, figuratively) To temper an action or decision.
   • 1992, Rudolf M[athias] Schuster, The Hepaticae and Anthocerotae of North America: East of the Hundredth Meridian, volume V, New York, N.Y.: Columbia University Press, →ISBN, page vii:

     With fresh material, taxonomic conclusions are leavened by recognition that the material examined reflects the site it occupied; a herbarium packet gives one only a small fraction of the data desirable for sound conclusions. Herbarium material does not, indeed, allow one to extrapolate safely: what you see is what you get […]

4. (transitive, figuratively) To imbue; to infect; to vitiate.
   • 1649, John Milton, Eikonoklastes, London: 1756, p. 30,

     With these and the like deceivable doctrines, he levens also his prayer.

   • 1716, Thomas Browne, Christian Morals, 2nd edition edited by Samuel Johnson, London: J. Payne, 1756, Part I, p. 7,

     […] pursue virtue virtuously: leven not good actions, nor render virtues disputable. Stain not fair acts with foul intentions […]

5. To rise or become larger. (Can we add an example for this sense?)

• leven (obsolete)

• leavened
• leavening
• unleavened

• yeast

leaven

1. plural of leaf