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

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

In Mint, Regan has widened the aperture and secured a buzzy cast, including a rare TV acting performance from Ben Coyle-Larner AKA hip-hop star Loyle Carner. —Jesse Whittock, Deadline, 8 Oct. 2025

These Celestron Skymaster 20x80 binoculars let in enough light for regular skywatching, thanks to their massive 80mm apertures. —Chris McMullen, Space.com, 7 Oct. 2025

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

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