SI base unit units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter. For example, the "metre" (US English: "meter") has the symbol m, but the "kelvin" has symbol K, because it is named after Lord Kelvin and the "ampere" with symbol A is named after André-Marie Ampère. Several other units, such as the litre (US English: "liter"), are formally not part of the SI, but are accepted for use with SI. New definitions of the base units were approved on 16 November 2018, to take effect 20 May 2019. The
Conventional electrical unit not precisely the same as the SI definitions but very nearly equivalent). Conventional electrical units are based on defined values of the Josephson constant and the von Klitzing constant, which allow practical measurements of electromotive force and electrical resistance respectively. Conventional electrical units can be thought of as a scaled version of a system of natural units defined as having consequence: This is a more general (or less specific) version of either the particle physics "natural units" or the quantum chromodynamical system of units but that no unit mass is fixed. Like n.u. or QCD units, with conventional electrical units