substance vs stuff

substance and stuff both are nouns.

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

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

substance: the real physical matter of which a person or thing consists
stuff: the tangible substance that goes into the makeup of a physical object

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

substance: the choicest or most essential or most vital part of some idea or experience
stuff: a critically important or characteristic component

Other hyponyms of substance include bare bones, hypostasis, haecceity, quiddity, quintessence.

substance (noun)	stuff (noun)
the real physical matter of which a person or thing consists	miscellaneous unspecified objects
a particular kind or species of matter with uniform properties	unspecified qualities required to do or be something
the property of holding together and retaining its shape	a critically important or characteristic component
the idea that is intended	senseless talk
the choicest or most essential or most vital part of some idea or experience	information in some unspecified form
content communicating a message; what something is about	informal terms for personal possessions
considerable capital (wealth or income)	the tangible substance that goes into the makeup of a physical object
material of a particular kind or constitution

substance (verb)	stuff (verb)
	fill with a stuffing while cooking
	fill tightly with a material
	treat with grease, fill, and prepare for mounting
	overeat or eat immodestly; make a pig of oneself
	cram into a cavity
	obstruct
	press or force