American English

Definition of aperture noun from the Oxford Advanced American Dictionary



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  1. 1(formal) a small opening in something The soldier fired the rifle through a narrow aperture in a pile of sandbags.
  2. 2(technology) an opening that allows light to reach a lens, especially in cameras For flash photography, set the aperture at f.5.6. Open up the lens aperture to maximize the brightness of the shot. Binoculars of this aperture are very expensive.
See the Oxford Advanced Learner's Dictionary entry: aperture