standard electromotive force

Quantity defined by $E ° = − Δ r G ° n F = R T n F ln K °$ , where $Δ r G °$ is the standard Gibbs energy of the cell reaction in the direction in which reduction occurs at the right-hand electrode in the diagram representing the cell ('reduction at right'), $K °$ is the standard equilibrium constant for this reaction, $n$ its charge number, $F$ the Faraday constant, $R$ the gas constant and $T$ the thermodynamic temperature.

Source:

Green Book, 2nd ed., p. 58