aperture

noun

ap·​er·​ture ˈa-pər-ˌchu̇r 

ˈa-pə-,

-chər,

-ˌtyu̇r,

-ˌtu̇r

1

: an opening or open space : hole

entered the cave through a narrow aperture

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

Synonyms

• hole
• opening
• orifice
• crevice
• slit

Examples of aperture in a Sentence

We entered the cave through a narrow aperture.

The photograph was taken using a fast shutter speed and a large aperture.

Recent Examples on the Web

Synthetic aperture radar takes advantage of the fact that NISAR is moving. —Keith Cooper, Space.com, 23 July 2025

At the South Pole, with a new five-meter aperture microwave telescope plus an array of nine smaller telescopes and state-of-the-art detectors, CMB-S4 would take an ultradeep look at roughly 3 percent of the sky. —Nadia Drake, Scientific American, 22 July 2025

Smartphone users should use their mobile devices’ night mode feature and not use flash if possible, while observers with traditional cameras should use low apertures, wide-angle lenses and tripods for image stability. —Antonio Pequeño Iv, Forbes.com, 3 July 2025

Up close, with its apertures open, the T.50 looks both fabulously exotic and a masterpiece of packaging, somehow squeezing three people, 10.2 cubic feet of luggage space, and a V-12 engine into a footprint similar to a Porsche Boxster. —Tim Pitt, Robb Report, 9 July 2025

Word History

Etymology

Middle English, borrowed from Latin apertūra, from apertus, past participle of aperīre "to open" + -ūra -ure — more at aperient

First Known Use

15th century, in the meaning defined at sense 1

Kids Definition

aperture

noun

ap·​er·​ture ˈap-ə(r)-ˌchu̇(ə)r 

-chər

1

: an opening or open space : hole

2

a

: the opening in a camera lens that allows light through

b

: the diameter of the opening in a camera lens

Medical Definition

aperture

noun

ap·​er·​ture ˈap-ə(r)-ˌchu̇(ə)r, -chər, -ˌt(y)u̇(ə)r 

1

: an opening or open space

2

: the diameter of the stop in an optical system that determines the diameter of the bundle of rays traversing the instrument