# Why is \mathsf{} used for formal systems?

A lot of times I have seen well-respected members of this community edit posts (including mine) changing things like "ZFC" into "$\mathsf{ZFC}$".

It kind of makes sense, because formal systems like ZFC are almost universally considered to be mathematical objects.

Why, then, not just put dollar signs before and after "ZFC"? I mean, there is definitely a difference between:

I have seen 10 proofs of this theorem.

and:

The number $10$ is divisible by $2$.

What is so special about \mathsf{}? Is it common in the literature to use this font to denote formal systems?

• I don't know about formal systems, but I don't think it is typographically appropriate use dollar signs in this case. Consider for example $\sin(x)$ vs $sin(x)$. I also don't think that it should use the same typeface as in $\sin(x)$ because that is normally reserved for an operator, so a different one should be probably selected. Sometimes these things just arise by tradition. – JessicaK Apr 14 '16 at 13:41
• Since the option is available, I would in fact use $10$ in both of your highlighted sentences: I consider it more readable than the default numerals. – Brian M. Scott Apr 14 '16 at 21:56