void

Void is a term used to describe emptiness or the absence of content, value, or validity. It appears across disciplines to denote nothingness, nullity, or a lack of effect, and it is often contrasted with fullness, presence, or validity.

In mathematics and logic, the concept closest to "void" is the empty set, the unique set with no elements. In philosophy and computer science, void or null can indicate absence of a value or reference. The precise meaning depends on context and formal definitions.

In physics, a vacuum is space devoid of matter, though not perfectly empty due to quantum fluctuations. In cosmology, cosmic voids are vast regions with very low galaxy density between clusters, contributing to the large-scale structure of the universe.

In computing and programming languages, void is a type specifier for operations that produce no value. A function declared as returning void does not return data; a void pointer is a generic pointer type that can reference any data type, requiring casting to use the pointed-to value.

In law and contract law, something that is void is invalid from the outset and has no legal effect. A contract might be declared void if it lacks a required element or is formed under duress.

In everyday usage, void can denote an empty space or act as a verb meaning to cancel or invalidate, as in voiding a check or a form. The term carries a common thread of absence and nonexistence across different domains.