Let $M = (X, \mathcal{F}, \mu)$ be a D1158: Measure space such that

(i)	$f : X \to [0, \infty]$ is an D5610: Unsigned basic Borel function on $M$

Let $\lambda \in [0, \infty]$ be an D5237: Unsigned basic number.

Then \begin{equation} \lambda \mu \{ x \in X : f(x) > \lambda \} \leq \int_X f I_{\{ f > \lambda \}} \, d \mu \end{equation}