symbols, acronyms & abbreviations


microliter: micro- + liter, a millionth of a liter. Used without a period. A symbol in SI, the International System of Units.

The symbol L was adopted in the United States (as an alternative to “l”) to avoid confusion between the numeral “1” and the lowercase letter “l”, since these characters are the same or very similar in many fonts, including typewriting. “L” was approved as an alternative symbol by the CGPM in 1979 (Resolution 6).

Metric System of Measurement; Interpretation of the International System of Units for the United States.
Federal Register Dec. 20, 1990. (55 FR 522 42-522 45).

American National Standard ANSI/IEEE Std 268-1982, Metric Practice.


Barry N. Taylor and Ambler Thompson, editors.
The International System of Units (SI) pdf logo
NIST Special Publication 330, 2008 Edition.

“United States version of the English text of the eighth edition (2006) of the International Bureau of Weights and Measures publication Le Système International d’ Unités (SI)” This publication is the definitive guide for the United States, but the ultimate authority is the original, French version. For the symbol for the micro- see page 29; for the liter, page 32, especially footnote f.

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