Fiber (mathematics)

In mathematics, the fiber (US English) or fibre (British English) of an element ${\displaystyle y}$ under a function ${\displaystyle f}$ is the preimage of the singleton set ${\displaystyle \{y\}}$, that is

${\displaystyle f^{-1}(y)=\{x\mathrel {:} f(x)=y\}.}$