Definition of "Substrate" :

noun: 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."

noun: any stratum or layer lying underneath another

noun: a surface on which an organism grows or is attached

"The gardener talked about the proper substrate for acid-loving plants."

noun: the substance that is acted upon by an enzyme or ferment