An opening made by the pupil in the eye.

A manifold or topological space X on which G acts by symmetry in a transitive way.

A space transportation system developed by NASA consisting of a reusable winged orbiter, a set of recoverable booster rockets, and a fuel tank. / The reusable winged orbiter of this system.

Alternative spelling of double-spaced

(mathematics, geometry) A space where the principles of Euclidean geometry apply.

(functional analysis) A normed vector space which is complete with respect to the norm, meaning that Cauchy sequences have well-defined limits that are points in the space.

(mathematics, physics, dynamical system theory) Given a (dynamical) system, any topological space such that every point in the space's underlying set uniquely represents a state of the system and every possible state is represented by some point;

(initially derogatory) A subgenre of speculative fiction or science fiction that emphasizes space travel, romantic adventure, and larger-than-life characters often set against vast exotic settings.

(physiology) The portion of the respiratory tract that is ventilated but not perfused by pulmonary circulation.

the totality of information, especially that which is accessible online