One of my lecturers last year (a pharmacologist by training) used the symbol $\Omega ^m$ as a shorthand for equilibrium. He implied it was common practice but I've never come across it elsewhere. I was wondering if anyone else has encountered it?

  • $\begingroup$ Interesting, what chemistry course was it, a pharmachem? Where exactly was the symbol used: above an arrow like $\ce{A <=>[$Ω^m$] B},$ or in the text and formulas as well? $\endgroup$
    – andselisk
    Dec 24, 2019 at 11:51
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    $\begingroup$ Yes, it was a Chemical Pharmacology course. It wasn't used with equilibrium arrows, only in text. I've adopted it in all my notes to save me handwriting "equilibrium" every time. $\endgroup$
    – atbm
    Dec 24, 2019 at 12:08
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    $\begingroup$ I think the instructor is mistaken. Can you find this notation in any textbook. I haven't seen this notation for equilibrium in my life. $\endgroup$
    – AChem
    Dec 24, 2019 at 18:27
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    $\begingroup$ My A level chemistry teacher in 1978 also used this symbol to represent equilibrium but since then I have not come across this. $\endgroup$
    – Ian Taylor
    Nov 1, 2021 at 17:00

1 Answer 1


I would guess $Ω^m$ notation is a personal invention and I couldn't find any sources that would standardize it.

The choice of these symbols for abbreviating "equilibrium" may be justified that the glyph "Libra"originates from the Greek letter Omega Ω. Further, from Merriam–Webster Online:

Equilibrium contains a root from the Latin libra, meaning "weight" or "balance". As a constellation, zodiac symbol, and astrological sign, Libra is usually pictured as a set of balance scales, often held by the blindfolded goddess of justice, which symbolizes fairness, equality, and justice. Equilibrium has special meanings in biology, chemistry, physics, and economics, but in all of them it refers to the balance of competing influences.

Uppercase letter "m" is probably because $Ω^m$ is a shortened form (contruction) of a single word that ends in the same letter: equilibrium.


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    $\begingroup$ Yes, I did think that was the point of the m. I had no idea about Libra - that's really interesting. Thank you! $\endgroup$
    – atbm
    Dec 26, 2019 at 8:54

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