The identity on a set $X$ is the binary relation
\[\id_X = \{(x, x) : x \in X\}.\]
Note.βFor any set $X$, $\id_X$ is also a function and is known as the identity function.
The identity on a set $X$ is the binary relation
\[\id_X = \{(x, x) : x \in X\}.\]
Note.βFor any set $X$, $\id_X$ is also a function and is known as the identity function.