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

Biomass is carrying the first P-band synthetic aperture radar in space. —Matthew Glasser, ABC News, 30 Apr. 2025

The ultra-wide camera enjoys an aperture of f/2.0 and a wide 122-degree field of view. —PC Magazine, 24 Apr. 2025

Cassini used synthetic aperture radar (SAR) to look through Titan's thick atmosphere during these close encounters and found channels and large flat areas that are consistent with large bodies of liquid. —Julian Dossett, Space.com, 22 Apr. 2025

Engineers kept Moore’s Law—the doubling of transistor count every couple of years—alive for more than five decades by incrementally reducing the wavelength of light and expanding the numerical aperture of the imaging system used in lithography. —Jayson Stewart, IEEE Spectrum, 5 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