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
Lambda (unit) mL (a unit 1000 times larger). In pharmaceutical use, no abbreviation for a microlitre is considered safe. The recommended practice is to write "microlitre" in full. Lambda (unit) Lambda (written λ, in lowercase) is a non-SI unit of volume equal to 10m, 1 cubic millimeter (mm) or 1 microlitre (µL). Introduced by the BIPM in 1880, the lambda has been used in chemistry and in law for measuring volume, but its use is not recommended. This use of λ parallels the pre-SI use of µ on its own for a micrometre and γ for a microgram. Although the use of