It’s interesting that each letter of the Greek alphabet has a function so I just decided to list them here for fun! It’s interesting to see how many are actually are related. Note: these aren’t functions that are just denoted by these symbols. They are functions which are named after these symbols

Alpha function

Beta function

Gamma function

Delta function

Zeta function^{1}

Eta function^{2}

Theta function

Iota function^{3}

Lambda function

Mu function

Nu function

Xi function

Pi function

Sigma function^{4}

Tau function

Phi function

Chi function^{5}

Psi function

Omega function

^{1} Technically is any function that can be defined by infinite sum of powers but this is most common one (Riemann)

^{2} Another type of eta function also exists (Dedekind) but this was chosen due to its close relation to Zeta

^{3} Iota function set is set of all functions ever described

^{4} Technically called divisor function, sigma function assumes

^{5} There also exists a Legendre Chi function

If you want to learn more about any of these functions or see where I learned them from, refer to Wolfram Mathworld