substance vs leavening

substance and leavening both are nouns.

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

As nouns, leavening is a hyponym of substance; that is, leavening is a word with a more specific, narrower meaning than substance:

substance (noun)	leavening (noun)
the real physical matter of which a person or thing consists	an influence that works subtly to lighten or modify something
a particular kind or species of matter with uniform properties	a substance used to produce fermentation in dough or a liquid
the property of holding together and retaining its shape
the idea that is intended
the choicest or most essential or most vital part of some idea or experience
content communicating a message; what something is about
considerable capital (wealth or income)
material of a particular kind or constitution