Meaning of APERTURE in English

[ap.er.ture] n [ME, fr. L apertura, fr. apertus, pp. of aperire to open] (15c) 1: an opening or open space: hole

2. a: the opening in a photographic lens that admits the light b: the diameter of the stop in an optical system that determines the diameter of the bundle of rays traversing the instrument c: the diameter of the objective lens or mirror of a telescope

Merriam-Webster English vocab.      Английский словарь Merriam Webster.