Leaven | Mean of leaven in English Dictionary

/ˈlɛvən/

• Noun
• a substance (such as yeast) that makes dough rise and become light before it is baked
• something that makes a situation or mood less serious
1. a serious book that includes a few humorous stories as leaven
• Verb
• to make (something) less serious and often more exciting
1. Her jokes leavened [=lightened] the meeting's mood.
2. He needs to leaven his speeches with more humor.

• to add leaven to (bread, dough, etc.)
1. using yeast to leaven the dough/bread
2. Some breads are leavened [=made with leaven] and some breads are unleavened.