content vs substance

content and substance both are nouns.

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

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

content: the sum or range of what has been perceived, discovered, or learned
substance: the choicest or most essential or most vital part of some idea or experience

As nouns, content and substance are synonyms defined as:

content and substance: content communicating a message; what something is about

Other synonyms of content include message, subject matter.

content (noun)	substance (noun)
something (a person or object or scene) selected by an artist or photographer for graphic representation	the real physical matter of which a person or thing consists
the sum or range of what has been perceived, discovered, or learned	a particular kind or species of matter with uniform properties
content communicating a message; what something is about	the property of holding together and retaining its shape
(usually plural) everything that is included in a collection and that is held or included in something	the idea that is intended
the amount that can be contained	the choicest or most essential or most vital part of some idea or experience
the proportion of a substance that is contained in a mixture or alloy etc.	content communicating a message; what something is about
the state of being contented with your situation in life	considerable capital (wealth or income)
	material of a particular kind or constitution

content (adjective)	substance (adjective)
satisfied or showing satisfaction with things as they are

content (verb)	substance (verb)
satisfy in a limited way
make content