aperture

American  

[ap-er-cher] / ˈæp ər tʃər /

noun

1. an opening, as a hole, slit, crack, gap, etc.

2. Also called aperture stop.  Optics. an opening, usually circular, that limits the quantity of light that can enter an optical instrument.

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aperture British  

/ ˈæpətʃə /

noun

1. a hole, gap, crack, slit, or other opening

2. physics

   1. a usually circular and often variable opening in an optical instrument or device that controls the quantity of radiation entering or leaving it

   2. the diameter of such an opening See also relative aperture

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Other Word Forms

• apertural
  adjective
• apertured
  adjective

Etymology

Origin of aperture

1400–50; late Middle English < Latin apertūra an opening, equivalent to apert ( us ) opened (past participle of aperīre; aper ( i )- ( see aperient) + -tus past participle suffix) + -ūra -ure

Explanation

An aperture is an opening, usually a small one. “If you can thread the silk through that aperture and pull it out the other side, we can knot it and create a loop.” The most common place you’ll find aperture is when you’re talking about cameras or photography. In that case, an aperture refers specifically to the hole or opening in the lens that lets light through, which you can adjust (with the f-stop) to let in more or less light, resulting in a shallow or deep range of focus. A large aperture means only one tiny point of the photo will be in sharp focus, while a small aperture means that much of the background as well as the foreground will be in focus.

Example Sentences

ASML’s more advanced high numerical aperture EUV systems face stitching and design constraints that are slowing adoption from customers, Scemama notes.

From The Wall Street Journal • May 7, 2026

The 2025/26 away kit, manufactured by sportswear firm Hummel, features a repeating geometric pattern showing the lighthouse, viewed through a circular design resembling the sculpture's aperture.

From BBC • Apr. 24, 2026

He brought out Kehlani for “Folded,” another perfectly regal ballad that revels in a small aperture.

From Los Angeles Times • Apr. 13, 2026

The researchers also combined the CSV pre-seeding method with a slot-die coating process to fabricate a perovskite solar mini-module with an aperture area of 49.91 cm2.

From Science Daily • Mar. 1, 2026

He snapped the back of the camera shut and chose the appropriate shutter and aperture settings, which controlled the amount of light the film would be exposed to.

From "Shooting Kabul" by N. H. Senzai