The relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell.
Reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent. Oxidation and reduction occur simultaneously because for oxidation to take place the electrons lost by the substance that is oxidized must be accepted by atoms or ions of another substance. On the other hand, for reduction to occur the electrons gained by the substance that is being reduced must be transferred from the atoms of ions of another substance.