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, its variable aperture means the lens opening can be adjusted to let in more light, allowing for brighter images, greater depth of field, more vivid macro shots, and better performance in low-light conditions. —New Atlas, 21 Nov. 2025

Meanwhile, the 16 uses a 12MP ultra-wide camera with the same aperture and the same field of view. —PC Magazine, 19 Nov. 2025

The Hermes 900 carries various types of equipment, including EO/IR sensors, synthetic aperture radar, hyperspectral sensors, and laser designators. —Atharva Gosavi, Interesting Engineering, 13 Nov. 2025

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

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