I saw this written on a blackboard in the math department building the other day:

Gas Law: $PV=nRT$

Ideal Gas Law: $(P)(V)=(n)(R)(T)$

I know the ideal gas law is something from chemistry, but I'm assuming this is meant to be some sort of joke involving math. Any ideas?

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    $\begingroup$ It's simply, in commutative algebra, the ideal generated by a element $a$ is usually denoted $(a)$. $\endgroup$ – Bernard Dec 13 '15 at 1:54
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    $\begingroup$ And people say we don't have good jokes. Fancy that. $\endgroup$ – peter a g Dec 13 '15 at 2:46
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    $\begingroup$ I don't like "gassy" jokes so much ... $\endgroup$ – Hagen von Eitzen Dec 13 '15 at 10:44

In a ring, "$(a)$" is common notation for the principal ideal generated by $a$. (See https://en.wikipedia.org/wiki/Principal_ideal.)

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    $\begingroup$ But if the gas law is the equality $PV=nRT$, then the ideal gas law would be $(PV=nRT)$. The joke doesn't work. $\endgroup$ – Git Gud Dec 13 '15 at 13:02
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    $\begingroup$ @Git Ugh, no, that would be the gas law ideal. A horse race is a race for horses, and the ideal gas law is the gas law for ideals. $\endgroup$ – user856 Dec 13 '15 at 17:52

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