In measure theory, a conull set is a set whose complement is null, i.e., the measure of the complement is zero.. For example, the set of irrational numbers is a conull subset of the real line with Lebesgue measure.A related but slightly more complex example is given by Führ, p. 143.
A property that is true of the elements of a conull set is said to be true almost everywhere.. See p. 62 for an example of this usage.
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