Substrates

noun

1. What an enzyme acts upon.
2. A surface on which an organism grows, or to which an organism or an item is attached.

   "The rock surface of a rockpool is the substrate for a sessile organism such as a limpet."

3. An underlying layer; a substratum.
4. A language that is replaced in a population by another language and that influences the language imposed on its speakers.
5. (plating) A metal which is plated with another metal which has different physical properties.