Lambda (written λ, in lowercase) is a non- SI unit of

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The def ...

equal to 10⁻⁹ m³, 1 cubic millimetre (mm³) or 1 microlitre (μL). Introduced by the

BIPM The International Bureau of Weights and Measures (french: Bureau international des poids et mesures, BIPM) is an intergovernmental organisation, through which its 59 member-states act together on measurement standards in four areas: chemistry, ...

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 The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Uni ...

and γ for a

microgram In the metric system, a microgram or microgramme is a unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and United Kingdom whe ...

. Although the use of λ is deprecated, some clinical laboratories continue to use it. The standard abbreviation μL for a microlitre has the disadvantage that it can be misread as 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.Chris Langley and Yvonne Perrie (2014), ''Maths Skills for Pharmacy: Unlocking Pharmaceutical Calculations'', Oxford University Press,
p. 55.
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References

Units of volume Customary units of measurement Typographical symbols Non-SI metric units {{measurement-stub