Lambda (written λ, in lowercase) is a legitimate metric unit of volume equal to 10−9 m3, 1 cubic millimeter (mm3) or 1 microlitre (µL). Introduced by the BIPM in 1880,[1] the lambda has been used in chemistry[2] and in law for measuring volume, but its use is not recommended.[3]

This use of λ parallels the pre-SI use of µ on its own for a micrometre and γ for a microgram.[4][5] Although the use of λ is deprecated, some clinical laboratories continue to use it.[6] 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.[7]


  1. ^ Donald Fenna (2002), A Dictionary of Weights, Measures, and Units, Oxford University Press, ISBN 0198605226, p. 153.
  2. ^ "Units: L". University of North Carolina. Retrieved 2015-03-28. 
  3. ^ Carl A. Burtis and David E. BrunsTietz (2014), Fundamentals of Clinical Chemistry and Molecular Diagnostics, 7th ed., Elsevier Health Sciences, ISBN 0323292062, p. 114.
  4. ^ Lela Buckingham (2014), Fundamental Laboratory Mathematics: Required Calculations for the Medical Laboratory Professional, F. A. Davis, ISBN 0803641028, p. 48.
  5. ^ I. P. Alimarin and M. N. Petrikova (2013), Inorganic Ultramicroanalysis, Elsevier, ISBN 1483150488, p. xiv.
  6. ^ Barbara H. Estridge, Anna P. Reynolds, and Norma J. Walters (2000), Basic Medical Laboratory Techniques, 4th ed., Cengage Learning, ISBN 0766812065, p. 32.
  7. ^ Chris Langley and Yvonne Perrie (2014), Maths Skills for Pharmacy: Unlocking Pharmaceutical Calculations, Oxford University Press, ISBN 019968071X, p. 55.