Q: Notation indicating a number is negative, positive, or zero. We can indicate that $x$ is negative by writing $x<0$, that it is positive by writing $x>0$, or that it is zero by writing $x=0$.
Out of curiosity, are there other notations, such as an overset or underset, to say the same?

A: [Comment converted to answer]
Those conditions are precisely the definitions of a number being negative, positive, or zero.
You can always use or create equivalent statements, such as $x\in\mathbb R^+$ or $\operatorname{sgn}(x) = 1$ (the latter referring to the signum function which takes values $-1$, $1$, or $0$ corresponding to $x$ being negative, positive, or zero -- essentially, the "sign" of $x$).
