Overview
Lebesgue measurable sets are the subsets of {% \mathbb{R}^n %} that can be assigned a consistent measure. The concept is generalized as Measurable Sets
Definition
Let {% E \subset \mathbb{R}^n %}
then {% E %} is measurable if
then {% E %} is measurable if
{% m^*(A) = m^*(A\cap E) + m^*(A \backslash E) %}
for all {% A \subset \mathbb{R}^n %}
Almost Everywhere
A condition {% C(x) %} is said to hold almost everywhere if the set
{% x %} such that {% C(x) %} is false has measure {% 0 %}.