Leaven

Etymology

From Latin "levare" (to raise, to lighten), from "levis" (light in weight), via Old French "levain." A leavening agent lifts dough; figuratively, to leaven a grim speech or a dull room is to lift and enliven it.

verb · /LEV-un/
To make dough or batter rise by introducing a gas-producing agent such as yeast, baking soda, or sourdough starter.
What it names
The transformation that turns dense paste into airy bread — and serves as a metaphor for lightening anything heavy.
Example
Without something to leaven it, the flatbread stays flat and cracker-hard.
Related idea
Leavening depends on fermentation: the rising agent — yeast or a sourdough culture — exhales gas that gets trapped in the dough and lifts it.
verb · /LEV-un/
To permeate and lighten or enliven something otherwise heavy or dull.
What it names
the modifying of a mood or tone by adding something
Example
He leavened the grim report with a few dry jokes.
Related idea
As yeast lifts dough, a light touch lifts a heavy moment — countering gravitas with warmth.