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reduction potential

(Eh, ORP, pE, redox potential, oxidation/reduction potential)
(measure of a chemical species' tendency to acquire electrons)

Reduction potential (or redox potential, oxidation/reduction potential, ORP, pE, or Eh) is the tendency of a chemical species (atom or molecule) to acquire electrons, i.e., reduction such as in a redox reaction.

For Earth use, a standard reduction potentials are measured and recorded using a specific set of conditions to represent a plausible Earth-bound situation. A reduction potential depends upon factors such as temperature and pressure.