This refers to the _sign_ of a real number, $+$ or $-,$ and this itself can also be defined as the [Function](Analysis%20(index).md#Functions)
$\mathrm{sgn}(x)=\begin{cases}
-1,& x<0\\
0,& x=0\\
1,& x>0
\end{cases}$
In terms of the [[Heaviside function]] the signum is
$\mathrm{sgn}(x) = 2\Theta(x)-1$
#MathematicalFoundations/Numbers
#MathematicalFoundations/Analysis