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Total record count: 6269.

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Eng ID Term Definition
181
antenna
A conductor or system of conductors for radiating or receiving RADIO WAVES. Also called aerial.
182
antenna: directional
An ANTENNA for transmitting or receiving SIGNALS in, or from, a given direction.
183
antenna: omnidirectional
An ANTENNA having essentially uniform response in AZIMUTH and a directional pattern in ELEVATION.
184
antenna: screened
Any ANTENNA which is screened in some way to counteract disturbances.
185
antenna: unidirectional
An ANTENNA having a single well-defined direction of maximum radiation intensity or maximum GAIN.
186
anthelion
Pure white, rounded spot, but sometimes iridescent or surrounded by coloured rings or arcs, which appears on very rare occasions opposite th... more
Pure white, rounded spot, but sometimes iridescent or surrounded by coloured rings or arcs, which appears on very rare occasions opposite the SUN and at the same HEIGHT above the HORIZON.
187
anticline
An arch of stratified ROCK in which the LAYERS bend downward in opposite directions from the CREST.
188
anticyclone
Region of the ATMOSPHERE where the pressure is high relative to the surrounding region at the same LEVEL. It is represented on a SYNOPTIC CH... more
Region of the ATMOSPHERE where the pressure is high relative to the surrounding region at the same LEVEL. It is represented on a SYNOPTIC CHART by a system of ISOBARS at a specified LEVEL or of CONTOURS at a specified pressure which enclose relatively high values of pressure or LEVEL. Also called high.
189
antimeridian
The MERIDIAN which is 180 deg of LONGITUDE from a given MERIDIAN. One MERIDIAN with its antimeridian constitute a complete GREAT CIRCLE.
190
antipode(s)
Place(s) on the surface of the EARTH directly opposite to each other.
191
antiselena
Luminous PHENOMENON analogous to ANTHELION, the luminary being the MOON.
192
anti-trade
Air current with a westerly component which in various subtropical regions of either hemisphere sometimes blows above the TRADE WIND.
193
aperture: relative
For a photographic or telescopic LENS, the ratio of the EQUIVALENT FOCAL LENGTH to the diameter of the ENTRANCE PUPIL. Expressed as f: 4.5; ... more
For a photographic or telescopic LENS, the ratio of the EQUIVALENT FOCAL LENGTH to the diameter of the ENTRANCE PUPIL. Expressed as f: 4.5; also called f-number, f-stop, or speed of lens.
194
aperture of antenna
The diameter of a reflector antenna, usually expressed in units of WAVE LENGTH.
195
aperture stop
The physical element (such as a DIAPHRAGM, or lens periphery) of an OPTICAL SYSTEM which limits the size of the PENCIL of RAYS traversing th... more
The physical element (such as a DIAPHRAGM, or lens periphery) of an OPTICAL SYSTEM which limits the size of the PENCIL of RAYS traversing the system. Also called the stop. Diameter of that part of the LENS actually used.
196
apex
The top, PEAK, or highest point of something, as of a MOUNTAIN. See also VERTEX.
197
apex: solar
The point of the CELESTIAL SPHERE towards which the SOLAR SYSTEM as a whole is moving. It lies in the CONSTELLATION of Hercules.
198
aphelion
That orbital point farthest from the SUN when the SUN is the centre of attraction, as opposed to PERIHELION.
199
aphotic
(adj.). Without light.
200
apochromatic lens
A LENS that has been corrected for CHROMATIC ABERRATION for at least three colours.