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
• 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

Rather than recognizing the history of autism research, the true needs of parents, and a proper scientific method, the administration has narrowed the aperture. —Dr. Sunny Patel, Time, 2 Oct. 2025

It's designed for deep sky astrophotography, while also being well suited to image capture of the Sun and Moon – with its camera system built around a Sony IMX585 sensor and 50-mm aperture. —New Atlas, 30 Sep. 2025

This month, Tapestry laid out the strategic plan that will guide it for the next three years, focusing pushing Coach toward $10 billion in sales and opening the customer aperture, targeting not just women who bought bags last year, but also women who could have. —Evan Clark, Footwear News, 29 Sep. 2025

The ring is dedicated to aperture adjustment for the Fujifilm and Sony versions of the lens, while the ring on the Canon version supports a configurable function (aperture, EV, or ISO). —PC Magazine, 23 Sep. 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