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

If applicable, low apertures and wide-angle lenses can also help grab good shots of the natural phenomenon. — Antonio Pequeño Iv, Forbes.com, 27 June 2026

And there's no question about which exposure mode you've got set at any time; it's shown (along with the aperture, shutter speed, ISO, and EV compensation) on the monochrome info display on the top plate. — Jim Fisher, PC Magazine, 25 June 2026

And this is the only model in the range to offer six-step adjustment of the aperture for even more control over onscreen lights and darks. — Paul Ridden june 22, New Atlas, 22 June 2026

About one year into its mission and far from Earth, in October 2024, the Psyche spacecraft linked up communications with the 5-meter aperture Hale Telescope at Caltech’s Palomar Observatory in San Diego County. — Eric Berger, ArsTechnica, 22 June 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