Conull set explained

In measure theory, a conull set is a set whose complement is null, i.e., the measure of the complement is zero.^[1] For example, the set of irrational numbers is a conull subset of the real line with Lebesgue measure.^[2]

A property that is true of the elements of a conull set is said to be true almost everywhere.^[3]

Notes and References

1. .
2. A related but slightly more complex example is given by Führ, p. 143.
3. . See p. 62 for an example of this usage.