1. A substance used to produce fermentation in dough or a liquid
   "Yeast is a common leaven agent used in bread making";
   - leavening
    
2. An influence that works subtly to lighten or modify something
   "His humour acted as a leaven in the tense meeting";
   - leavening

1. Cause to puff up with a leaven
   "The yeast leavened the bread dough";
   - raise, prove

Derived forms: leavened, leavening, leavens

Type of: bring up, elevate, get up, imponderable, lift, raise

Encyclopedia: Leaven