tera. The metric prefix that means a million million, or 1 x 1012.
terbium. A soft, silvery-gray, rare-earth, metallic chemical element. Terbium’s symbol is Tb, its atomic number is 65, and its atomic weight is 158.924. Terbium is used in the manufacture of semiconductor devices and in laser technology.
terminal (computer system). The device in a computer system that allows the human operator to interface with the computer. A computer terminal normally contains a video display similar to a television screen and a keyboard much like the keyboard of a typewriter.
terminal (electrical wiring component). A device that is crimped or soldered onto the end of an electrical wire to allow the wire to be attached to a component or terminal strip. Electrical wire terminals may be in the form of a ring, a spade, or a flag, and they may be insulated or uninsulated. See illustration for solderless connections.
terminal radar service area. See TRSA.
terminal strip (electrical system component). A strip of insulating plastic material that contains a number of threaded studs to which electrical wires can be attached. Ring-type terminals on the wires are slipped over the studs and secured with a lock washer and nut. Some terminal strips have barriers between adjacent studs to keep the wires from shorting between the studs.
terminal velocity. The maximum speed a freely falling object can reach when falling through the air. At the terminal velocity, the wind resistance trying to slow the object down exactly balances the force of acceleration trying to speed the object up.
terminal VOR (electronic navigation facility). A low-powered VOR that is normally located on an airport.
terminating decimal. A decimal fraction which can be expressed as a definite number. The fraction 2/5 produces a terminating decimal, 0.4. A fraction that cannot be expressed as a definite number is called a repeating decimal. The fraction 1/3 is a repeating decimal, and it is equivalent to 0.333333333… .
terneplate. Thin sheets of steel protected from rust with a thin coating of lead. The lead coating allows terneplate to accept solder so the seams in a tank made from terneplate can be made leakproof.
terrestrial radiation (meteorology). The total infrared radiation emitted by the earth and its atmosphere.
test club (type of propeller). A wide-blade, short-diameter propeller used on a reciprocating engine when it is run in a test stand. A test club applies a specific load to the engine and forces the maximum amount of air through the cylinder cooling fins.
tetrahedron (wind direction indicator). A large, lightweight framework made in the shape of a tetrahedron, a triangular-shaped solid. The framework is covered with thin metal, wood, or fabric and is painted a bright color. It is mounted on a pivot so it is free to swing with the wind, and is installed near the center of an airport beside the runway, where it is easily visible from the air. The tetrahedron always points into the wind and shows pilots approaching the airport the correct direction to make their landing approach.
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