An example of an aperture is the opening in a camera lense.
An aperture between the mountains. --Gilpin.
The back aperture of the nostrils. --Owen.
If the generatrix makes an angle θ to the axis, then the aperture is 2θ.
Origin of aperture
- Middle English from Latin apertūra from apertus past participle of aperīre to open wer-4 in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition