from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An opening, such as a hole, gap, or slit.
  • n. A usually adjustable opening in an optical instrument, such as a camera or telescope, that limits the amount of light passing through a lens or onto a mirror.
  • n. The diameter of such an opening, often expressed as an f-number.
  • n. The diameter of the objective of a telescope.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall.
  • n. Something which restricts the diameter of the light path through one plane in an optical system.
  • n. 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. e.g. a telescope may have a 100 cm aperture.
  • n. 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.
  • n. The maximum angle between the two generatrices.

from the GNU version of the Collaborative International Dictionary of English

  • n. The act of opening.
  • n. An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole.
  • n. The diameter of the exposed part of the object glass of a telescope or other optical instrument.

from The Century Dictionary and Cyclopedia

  • n. The act of opening out or unfolding.
  • n. An opening; a hole, orifice, gap, cleft, or chasm; a passage or perforation; any direct way for ingress or egress.
  • n. In geometry, the space between two intersecting right lines.
  • n. In optics, the diameter of the exposed part of the object-glass in a telescope or other optical instrument.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a device that controls amount of light admitted
  • n. an man-made opening; usually small
  • n. a natural opening in something


Middle English, from Latin apertūra, from apertus, past participle of aperīre, to open; see wer-4 in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Latin apertūra ("opening"), from apertus, past participle of aperīre ("to open, uncover"), opposed to operīre ("to close, cover"). See aperient. (Wiktionary)


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  • In retailing the size of the aperture is often used to provide shoppers with clues about what is in a store.

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  • If in the walls surrounding this cavity a small aperture is made through which radiation issues, we obtain a radiation which is independent of the nature of the emitting body, and is wholly determined by the temperature.

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  • The aperture is 20 ft. wide, and is still widening.

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  • Josh: Well, we basically just looked up various words for different meanings and came up with the word aperture, which means an opening through which light is emitted.

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  • I was reading through a section of my post from yesterday this afternoon and noticed that I called aperture apenture.

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  • a part of this stream of air, on each side of the edge of the aperture is perpetually stopped by that edge; and thus

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  • The aperture is a window, and it seems to me that we’re hoping for a door; a way to Be in Being that is more involved, engaged, and shadow-throwing than mere picture-taking.

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  • The optical sleight of hand used by the astronomers combined the telescope's "adaptive optics" with a technique called aperture mask interferometry: using a a deformable mirror to rapidly correct for atmospheric distortions to starlight.

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  • All round this aperture, which is the mouth, imagine that there are placed a number of feelers forming a circle.



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  • I remember this word because a hole can be called a Portal, and the portal gun is made by Aperture Science.

    July 9, 2009

  • There's a photography magazine called this.
    It's got pictures in it.

    May 26, 2009