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 alleged suspension of information operations aimed at Russia and growing mistrust between the United States and its European allies open wide the aperture for foreign information and influence warfare. —Michael Miklaucic, Twin Cities, 5 Apr. 2025

The watch is presented in 18-karat white gold, with the winding crown positioned on the left side of the case and the date aperture at 9 o’clock. —Renan Botelho, Footwear News, 1 Apr. 2025

The watch also boasts an aperture on the dial for day and night indication of home time and local. —Roberta Naas, Forbes.com, 31 Mar. 2025

This type of optical diffraction makes small points of light take on the shape of the aperture and render as 14-point starbursts, but their tines lack definition, streaking out into multiple lines. —PC Magazine, 31 Mar. 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