1. <programming> In a reduction system, a closure is a data structure that holds an expression and an environment of variable bindings in which that expression is to be evaluated. The variables may be local or global. Closures are used to represent unevaluated expressions when implementing functional programming languages with lazy evaluation. In a real implementation, both expression and environment are represented by pointers. A suspension is a closure which includes a flag to say whether or not it has been evaluated. The term "thunk" has come to be synonymous with "closure" but originated outside functional programming. 2. <theory> In domain theory, given a {partially ordered set}, D and a subset, X of D, the upward closure of X in D is the union over all x in X of the sets of all d in D such that x <= d. Thus the upward closure of X in D contains the elements of X and any greater element of D. A set is "upward closed" if it is the same as its upward closure, i.e. any d greater than an element is also an element. The downward closure (or "left closure") is similar but with d <= x. A downward closed set is one for which any d less than an element is also an element. ("<=" is written in LaTeX as subseteq and the upward closure of X in D is written uparrow_D X). (1994-12-16)

(closures)

The closing or completion of a circuit by depressing a key or moving a switch.

The West Bank closure system is a series of obstacles including permanent and partially staffed checkpoints, concrete roadblocks and barriers, metal gates, earth mounds, tunnels, trenches, and an elaborate set of permit restrictions that controls and restricts Palestinian freedom of movement.

In computer science, syntactic closures are an implementation strategy for a hygienic macro system. The term pertains to the Scheme programming language.

Lesbians Against Pit Closures (LAPC) were an alliance of lesbian women who came together to support the National Union of Mineworkers and various mining communities during the UK miners' strike of 1984–1985. They were formed after a schism in the Lesbians and Gays Support the Miners (LGSM) movement, in November 1984.

Women Against Pit Closures was a political movement supporting miners and their families in the UK miners' strike of 1984–1985. The movement is credited with bringing feminist ideas into practice in an industrial dispute and empowering women to take a public role in a community with a male-dominated sphere.