An opening, gap, or hole, usually small and narrow
Something which restricts the diameter of the light path through one plane in an optical system.
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.
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.
The maximum angle between the two generatrices.
A plant of the genus Iris, common in the northern hemisphere, and generally having attractive blooms (See Iris (plant)).
The contractile membrane perforated by the pupil, which adjusts to control the amount of light reaching the retina, and which forms the colored portion of the eye (See Iris (anatomy)).
A diaphragm used to regulate the size of a hole, especially as a way of controlling the amount of light reaching a lens.
A rainbow, or other colourful refraction of light.
A constricted opening in the path inside a waveguide, used to form a resonator.
The inner circle of an oscillated color spot.
or door}} To open or close in the manner of an iris.
