Let $M = (X, \mathcal{F}, \mu, T)$ be a D2827: Measure-preserving system such that

(i)	$f : X \to Y$ is a D201: Measurable map on $M$

Then $f$ is almost stationary on $M$ if and only if \begin{equation} f \circ T \overset{a.e.}{=} f \end{equation}