sourdough vs leavening

sourdough and leavening both are nouns.

Word	Noun	Adjective	Verb	Adverb
sourdough	Yes	No	No	No
leavening	Yes	No	No	No

As nouns, leavening is a hypernym of sourdough; that is, leavening is a word with a broader meaning than sourdough:

sourdough: a leaven of dough in which fermentation is active; used by pioneers for making bread
leavening: a substance used to produce fermentation in dough or a liquid

Other hypernyms of sourdough include leaven.

sourdough (noun)	leavening (noun)
a settler or prospector (especially in western United States or northwest Canada and Alaska)	an influence that works subtly to lighten or modify something
a leaven of dough in which fermentation is active; used by pioneers for making bread	a substance used to produce fermentation in dough or a liquid