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?
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1$\begingroup$ 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 $x$. $\endgroup$– MPWMay 12, 2021 at 15:44
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$\begingroup$ @MPW Sounds like a great answer. If you post it as one, I will mark it. I definitely see how $x\in\mathbb{R}^+$ makes sense. $\endgroup$– OliverMay 12, 2021 at 16:58
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$\begingroup$ Consider $x\in\mathbb R^{>0}$ $\endgroup$– J. W. TannerMay 12, 2021 at 20:51
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[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 $x$).
