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

However, a telescope with an aperture of 8-inches or more will reveal Uranus as a tiny blue dot in the eyepiece under good atmospheric conditions. —Anthony Wood, Space.com, 5 Nov. 2025

Under Baer, Stitch Fix has been opening the aperture and is letting consumers get larger fixes on their own timetables as well as shipments based on a theme or built around a purchase through the platform’s freestyle service. —Evan Clark, Footwear News, 3 Nov. 2025

Capella Space, Umbra, and ICEYE provide synthetic aperture radar satellites commercially—another improbability is that there is not just one but multiple commercial SAR companies in the world. —Literary Hub, 28 Oct. 2025

At its center, the lens scores in the outstanding range at its maximum aperture (5,700 lines), though its edges and corners aren't as clear and bring the average score down into the excellent range for a 60MP chip (4,400 lines). —PC Magazine, 12 Oct. 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