(statistics) A hypothesis set up to be nullified or refuted in order to support an alternative hypothesis. When used, the null hypothesis is presumed true until statistical evidence in the form of a hypothesis test indicates otherwise. Therefore, the null and the alternative hypothesis must be mutually exclusive and exhaustive.

In a closed space-time, especially for an Einstein cylinder, null infinity for a given point is the limit of convergence of the light cone most distant from the given point. That is, it is the limit of a set of points that each have a time-like separation from every point that has a space-like separation from the given point.

(idiomatic, law) invalid, cancelled, unenforceable

(topology, of a map) Homotopic to a constant map.

plural of null anaphora

plural of null set

(mathematics, stochastic processes, of a state) persistent with finite expected return time.

A pro-drop language that may frequently leave out subject pronouns that are implied by verbal conjugations, such as Persian, Hebrew, and many Slavic and Romance languages.

plural of null-subject language

(architecture, computing, design) A behavioural design pattern that describes the uses of null objects and their behavior (or the lack of them).