General English

General Science

  • noun a lens diaphragm that allows the amount of light that reaches film to be regulated
  • noun an opening in a device that allows a specific amount of light or a signal to pass through it


  • The effective light-gathering diameter of a telescope lens or mirror, or other devices used for other wavelengths. The amount of light or other radiation gathered increases with the square of the aperture, in other words with the total area of the light-gathering surface.


  • noun an opening in a device that allows a certain amount of light or a signal to pass through it


  • In construction, any opening left in a wall for a door, window, or for ventilation.


  • An opening, such as a hole, gap, slit, vent, port, mouth, outlet, or perforation, through which electrons, light, waves, or any form of radiant energy may pass. Also called orifice (1).
  • The opening by which light enters, or through which it travels, of an optical device or system, such as a telescope or scanner. Such an opening may be in any shape, but is usually circular, rectangular, or elliptical.
  • In an antenna, the opening through which the radiated energy passes.
  • In a speaker, a port in the enclosure which increases and extends the reproduction of low frequencies.

Media Studies

  • noun the hole at the centre of a lens which admits light, measured in f-stops. It may be increased or decreased in size to alter the exposure of the film.


  • noun a partially-enclosed rounded white space in a letter such as ā€˜cā€™ or ā€˜Sā€™