单位的写法上常出现的问题是数字和单位之间不用空格, like 3.3 mg not 3.3mg, 4.0 mL not 4.0mL. 体积liter 缩写成L, 不用小写l.



  1. Symbols or abbreviations do not have a period (.) unless at the end of a sentence.
  2. Small letters (lower case) are generally used, except for symbols derived from the name of a person. Exceptions are liter, which is L, and molarity, which is M.
  3. The singular and plural forms of a symbol are the same. For example, 2 g not 2 gs, 2 mL not 2 mLs.
  4. A space separates the number and the symbol, like 1.2 s, 45 mM, 37 oC. Exceptions are the symbols for plane angular degrees, minutes and seconds (, ′ and ″). There will be no space between, like 45o, 5', 23".
  5. Symbols for derived units formed from multiple units by multiplication are joined with a space or center dot (), e.g. "N m" or "Nm".
  6. Symbols formed by division of two units are joined with a slash or given as a negative exponent. For example, the "meter per second" can be written "m/s", "m s−1", "ms−1" or a slash should not be used if the result is ambiguous, i.e. "kgm−1s−2" is preferable to "kg/ms".
  7. Some commonly used units:

kg, g, mg, mg, ng, pg

L, mL, mL, nL

mg/mL, mg/mL, ng/mL; better not use g/L, mg/L

mM, mM, nM, better not use mmol/L, mmol/L

M for molar, mol for mole

h for hours, min for minutes, s for seconds, m for meter

m, cm, mm

A, K, Hz, J, W, V, N, W