Notation (or Name) of the function which is $0$ at $x=0$ and $1$ otherwise Is there a traditional notation or name of this function:
$$
\epsilon (x)  = \begin{cases}
0 & \textrm{ if }x = 0 \\
1 & \textrm{ if }x \neq 0
\end{cases}
$$
I know one can use  Indicator function $1_{A}(x)$ for $A = \mathbb{R} - \{0\}$, but I still want to know if there is a traditional, simpler, notation for it.

The Kronecker delta function $\delta_{ij}$ is $1$ when $i=j$ and $0$ otherwise, so $\epsilon(x)=1-\delta_{0,x}$.
