Definition:Proportion/Inverse

Definition
Two real variables $x$ and $y$ are inversely proportional iff their product is a constant:
 * $\forall x, y \in \R: x \propto \dfrac 1 y \iff \exists k \in \R, k \ne 0: x y = k$

Also known as
The term proportion is more usually known nowadays by the word proportionality.