Algebraic Geometry/Functions

A function is a relation mapping one set (the domain) to another (the codomain) such that every element in domain has a unique image in its co-domain.

Examples of functions would include $2x+3y=9$, $4x+7z=8$

function is denoted by symbol $f(x)$ or $g(x)$ where $x$ is the independent variable and function are written as $f(x)=7x+9$