substrate has 1 distinct synonym spread across 3 of its 4 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 substance that is acted upon by an enzyme or ferment
a surface on which an organism grows or is attached
“the gardener talked about the proper substrate for acid-loving plants”
Synonyms, antonyms and the broader and narrower relations for substrate come from Princeton University’s WordNet. Full sources and licences.
an indigenous language that contributes features to the language of an invading people who impose their language on the indigenous population
“the Celtic languages of Britain are a substrate for English”