?symbol

$\text{If the dependence is linear, i.e. $x = \alpha y,~\alpha \in \mathbb{C}$, you can write $x \sim y$}\\ \text{Otherwise I would just write $x=f(y).\\$ I don't know of any single symbol that expresses it.}$

Thanks Rom,

Yes I like

x=f(y)     for x depends on y