Null (Mathematics)

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In mathematics, null usually means zero. For example, in a vector space the null vector, is the zero vector, in set theory, the null set, is the set with zero elements, and in measure theory, a null set, is a set with zero measure.

A mathematical mapping is said to be null potent (or nilpotent) if repeated application can map the whole domain into the null element.

A null space of a mapping is the part of the domain that is mapped into the null element of the image (the inverse image of the null element).

In statistics, a null hypothesis is a proposition presumed true unless statistical evidence indicates otherwise. Often it simply asserts the absence of something — for example it may say that a new drug being tested has no effect.

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