The potential of a polarographic or voltammetric indicator electrode at the point, on the rising part of a polarographic or voltammetric wave, where the difference between the total current and the residual current is equal to one-half of the limiting current. The quarter-wave potential, the three-quarter-wave potential, etc., may be similarly defined.
Source:
PAC, 1985, 57, 1491. 'Recommended terms, symbols, and definitions for electroanalytical chemistry (Recommendations 1985)' on page 1502 (https://doi.org/10.1351/pac198557101491)