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 )- ( 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

Narrator Jodie Foster widens the film’s aperture a bit early on, referring to the period “between Watergate and the Bicentennial” as the documentary’s focus.

From The Wall Street Journal • Dec. 18, 2025

A camera’s aperture widens during filming to capture the full spectacle.

From Salon • Aug. 23, 2025

A hermit crab will inspect a shell with care, running antennae and claws over its contours, before delicately lowering its rear end into the aperture.

From Slate • Aug. 19, 2025

Pushing the aperture or the F-stop down as low as possible allows the most light in, and he suggests setting the ISO as high as possible without adding grain to the image.

From Los Angeles Times • Jul. 18, 2024

Within the ranks of his arcane field—an advanced technology called synthetic aperture radar, or SAR—he is an eminence.

From "Into the Wild" by Jon Krakauer