Symbols:Greek/Phi

Euler Phi Function

 * $\phi \left({n}\right)$

Golden Mean

 * $\phi$

Mapping

 * $\phi \left({x}\right)$

The Greek letter $\phi$, along with $\psi$ and $\chi$ and others, is often used to denote a general mapping.

In the context of abstract algebra, it often denotes a homomorphism.