Definition:Homogeneous Function/Real Space/Zero Degree

Definition
Let $f: \R^2 \to \R$ be a real-valued function of two variables.

$f \left({x, y}\right)$ is a homogeneous function of degree zero or of zero degree :
 * $\forall t \in \R: f \left({t x, t y}\right) = t^0 f \left({x, y}\right) = f \left({x, y}\right)$