Definition:Inverse Entourage

Definition
Let $S$ be a set.

Let $\mathcal U$ be a quasiuniformity on $S$.

Let $u \in \mathcal U$ be an entourage of $\mathcal U$.

Then the inverse entourage $u^{-1}$ is defined as:
 * $u^{-1} := \left\{{\left({y, x}\right): \left({x, y}\right) \in u}\right\}$

Also see

 * Inverse relation, which is consistent with this definition.