In biochemistry, a compound or mixture of compounds acted on by an enzyme. The term also refers to a substance such as agar that provides the nutrients for the metabolism of microorganisms. Since the enzyme systems of microorganisms regulate their metabolism, the essential meaning is the same.
The substance acted upon by an enzyme or ferment.
The inactive supporting material used in a manufacturing process. In circuit boards, it is the base to which the traces (foil areas) are attached. In tapes and disks, it is the material on which the magnetic particles are fused.