In mathematics, given a locally Lebesgue integrable function f on \mathbb {R} ^{k}, a point x in the domain of f is a Lebesgue point if {\displaystyle \lim _{r\rightarrow 0^{+}}{\frac {1}{\lambda }}\int _{B}\!|f(y)-f(x)|\, \mathrm {d} y=0.} Wikipedia