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
• perforation

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

The camera connects to your phone via Bluetooth in an instant and allows for full manual aperture, shutter, exposure compensation, and focus control. —PC Magazine, 20 June 2025

For example, how far is the aperture of the zone around the 11 host cities? —Adam Crafton, New York Times, 20 June 2025

Photography experts told National Geographic a wide-angle lens and an aperture or F-stop of four or lower are recommended, though other settings like ISO and shutter speed will likely need to be adjusted depending on the strength of the aurora borealis. —Ty Roush, Forbes.com, 19 June 2025

For those with more advanced gear, experts recommend using a wide-angle lens with an aperture of f/4 or lower, setting the focus to the furthest possible to do the scene justice. —Valerie Mesa, People.com, 29 May 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