What's the definition of substrate?
A substrate is a substance to which another substance is applied; its definition varies in different sciences. In biology, it is a medium on which flora, fauna or fungi lives. In chemistry, it's a molecule acted upon by an enzyme. In geology, it's the layer of rock found beneath the soil.
According to Oxford Languages, substrate is a noun meaning: an underlying substance or layer. Another specific definition is: the surface or material on, or from which, an organism lives, grows, or obtains its nourishment. Or, the substance on which an enzyme acts.