Wikipedia - Standard electrode potential (en) standard electrode potential, $$E^{\unicode{x26ac}}$$

https://doi.org/10.1351/goldbook.S05912
The value of the standard emf of a cell in which molecular hydrogen under @[email protected] is oxidized to solvated protons at the left-hand electrode.
Source:
Green Book, 2nd ed., p. 59 [Terms] [Book]