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 of aperture

• 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

On the plus side, flare is not an issue at any aperture. —Jim Fisher, PC Magazine, 6 Apr. 2026

The new Calibre 1150 was designed using 3-D modeling such that nearly all functions are easily engaged and adjusted via three pushers fitted within and flanking the crown, while all calendar functions are displayed via dedicated apertures in order to minimize visual clutter. —Oren Hartov, Robb Report, 4 Apr. 2026

Rauschenberg’s experiments with Weil opened him up, like an aperture. —Hilton Als, New Yorker, 4 Apr. 2026

Your tongue might fall back into your throat, or the throat itself might relax too much, narrowing the aperture for air to get in and causing any number of the surrounding structures to vibrate. —Gilad Edelman, The Atlantic, 15 Mar. 2026

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