# What symbol should be used for the Michaelis constant? [closed]

I have found two different abbreviations for the Michaelis constant: $K_\mathrm M$ with capital subscript M, and $K_\mathrm m$ with a regular m. Which form is better for use in an article to be published?

## closed as primarily opinion-based by A.K., Mithoron, Todd Minehardt, aventurin, DSVAJul 1 '18 at 23:46

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• Whatever form that the editors want. – MaxW Jun 30 '18 at 22:08
• Many journals or scientific societies have a list of recommended abbreviations. – Karl Jul 1 '18 at 11:07

In page 66 of the 2005 Green Book ("Quantities, Units and Symbols in Physical Chemistry"), IUPAC recommends that $K_\mathrm M$ be used as the symbol for the Michaelis constant. Note that $K$ should be italicised whereas $\mathrm{M}$ should not be italicised.
Thanks to Loong, who points out that the ACS Style Guide (Chapter 10, p 186) actually suggests $K_\mathrm m$. The Style Guide, however, also states that it is "not intended to be exclusive; alternative choices, in many cases, are acceptable".