aperture
1. (window) The portion of a data record which is selected for specifying operators for use on the data set, e.g. operators such as autocorrelation functions and filters are applied by apertures on seismic records.

2. In a mollusc (Mollusca) shell, the opening through which the soft parts of the animal emerge. It is often a simple, circular opening, but is modified in some genera. In gastropods (Gastropoda), where the aperture is circular or elliptical it is said to be ‘holostomatous’ or ‘entire’; where it is notched (to accommodate a siphon) it is said to be ‘siphonostomatous’. In cephalopods (Cephalopoda), the aperture may be indented or notched at the ventral margin by a hyponomic sinus, which houses the hyponome. Some compressed ammonites (Ammonoidea) possess a pair of lateral shell extensions (lappets) on either side of the aperture.

ap·er·ture / ˈapərˌchər/ • n. chiefly technical an opening, hole, or gap: the bell ropes passed through apertures in the ceiling. ∎  a space through which light passes in an optical or photographic instrument, esp. the variable opening by which light enters a camera.

aperture. Opening in a wall for access, the admission of light or air (or both), or for defence or aesthetic reasons. Its sides are jambs, its top a head, lintel, or arch; and its bottom the cill.

aperture In photography, a hole that allows light to pass through the lens onto the film. Modern cameras usually have a diaphragm aperture which works like the iris of a human eye. The photographer can widen or narrow the diaphragm according to a series of points on the lens dial called ‘f-numbers’ or ‘f-stops’. The individual f-numbers represent the focal length of the lens divided by the diameter of the aperture. As the aperture narrows, it gives a longer depth of field.

aperture XV. — L. apertūra, f. apert-, pp. stem of aperīre; see prec., -URE.