aperture

US /ˈæp.ɚ.tʃɚ/
UK /ˈæp.ɚ.tʃɚ/
"aperture" picture
1.

a small opening or hole, especially one through which light or air may pass

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The camera's aperture controls the amount of light entering the lens.
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There was a small aperture in the wall, allowing us to peek through.
:
openingholegapslitvent