The part of the physical universe that is known by observation or inference.

(astronomy) The extent of a universe within the cosmological horizon of an observer.

plural of known universe

plural of observable universe

(logic) The set of all ground terms that may be formed (even recursively) using any of the constants and functions which appear in a given set of formulae. (If there is no constant in that given set of formulae, then designate one default constant as being usable for the aforementioned purpose.)

(astronomy, astrophysics) A theory that describes and seeks to explain the seemingly increasing rate of the expansion of the universe.

plural of accelerating universe

(mathematics, category theory) A kind of universal set whose elements follow the rules of Zermelo–Fraenkel set theory, and for which, with respect to an arbitrary set, an instance of its kind which has that set as a member may be posited to exist through an additional Tarski–Grothendieck axiom (which is not part of ZF but augments it, yielding Tarski–Grothendieck set theory).

plural of Grothendieck universe

plural of meta-universe