plural of open door

(idiomatic) To lead to opportunities or (social) advantages.

plural of open valley

(education) Referring to exams in which external resources such as textbooks, glossaries, study notes, calculators, etc. may be used.

(idiomatic) Something of which salient aspects are obvious or easily interpreted.

plural of open cluster

plural of open book

plural of open compound

(uncountable) A chess opening characterized by the moves 1.e4 e5, in which both White and Black move their king's pawn to the fourth rank with their first move.

(television) An opening segment shown before the opening credits.