# Definition:Real Function/Two Variables

## Definition

Let $f: S \times T \to \R$ be a mapping where $S, T \subseteq \R$.

Then $f$ is defined as a (real) function of two (independent) variables.

The expression:

$z = f \left({x, y}\right)$

means:

(The dependent variable) $z$ is a function of (the independent variables) $x$ and $y$.