SI base unit

The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units are derived. The SI base units and their physical quantities are:

The SI base quantities form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology. However, in a given realization in these units they may well be interdependent, i.e. defined in terms of each other.

The names and symbols of SI base units are written in lowercase (e.g. metre (US English: meter) has the symbol m), except the symbols of those named after persons which are written with an initial capital letter (i.e., the kelvin after Lord Kelvin has the symbol K and the ampere after André-Marie Ampère has the symbol A).

Many other units, such as the litre (US English: liter), are formally not part of the SI, but are accepted for use with SI.