aperture (plural apertures)
- An opening, gap, or hole, usually small and narrow
- an aperture in a wall
- 1860, Samuel Hannaford, Sea and River-side Rambles in Victoria Chapter 7
- In the centre of the fleshy membrane is an aperture leading into a deep cavity, at the bottom of which is placed a prominent piston that may be retracted by muscular fibres provided for the purpose.
- (optics) Something which restricts the diameter of the light path through one plane in an optical system.
- (astronomy, photography) The diameter of the aperture (in the sense above) which restricts the width of the light path through the whole system. For a telescope, this is the diameter of the objective lens.
- This telescope has a 100cm aperture.
- (spaceflight, communications) The (typically) large-diameter antenna used for receiving and transmitting radio frequency energy containing the data used in communication satellites, especially in the geostationary belt. For a comsat, this is typically a large reflective dish antenna; sometimes called an array.
- (mathematics, rare, of a right circular cone) The maximum angle between the two generatrices.
- If the generatrix makes an angle θ to the axis, then the aperture is 2θ.
- French: ouverture
- German: Öffnung
- Italian: apertura
- Portuguese: abertura
- Russian: отве́рстие
- Spanish: abertura