substance has 22 distinct synonyms spread across 5 of its 8 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the real physical matter of which a person or thing consists
“DNA is the substance of our genes”
the choicest or most essential or most vital part of some idea or experience
“the gist of the prosecutor's argument”
material of a particular kind or constitution
“the immune response recognizes invading substances”
considerable capital (wealth or income)
“he is a man of means”
what a communication that is about something is about
the property of holding together and retaining its shape
“wool has more body than rayon”
a particular kind or species of matter with uniform properties
“shigella is one of the most toxic substances known to man”
Synonyms, antonyms and the broader and narrower relations for substance come from Princeton University’s WordNet. Full sources and licences.