Meaning of APERTURE in English

noun Etymology: Middle English, from Latin apertura, from apertus, past participle of aperire to open Date: 15th century an opening or open space ; hole , 2. the opening in a photographic lens that admits the light, the diameter of the stop in an optical system that determines the diameter of the bundle of rays traversing the instrument, the diameter of the objective lens or mirror of a telescope

Merriam Webster. Explanatory English dictionary Merriam Webster.      Толковый словарь английского языка Мерриам-Уэбстер.