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lubrication

(Encyclopedia)lubrication, introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, liquid...

guided missile

(Encyclopedia)guided missile, self-propelled, unmanned space or air vehicle carrying an explosive warhead. Its path can be adjusted during flight, either by automatic self-contained controls or remote human control...

rapid transit

(Encyclopedia)rapid transit, transportation system designed to allow passenger travel within or throughout an urban area, usually employing surface, elevated, or underground railway systems or some combination of t...

navy

(Encyclopedia)navy, originally, all ships of a nation, whether for war or commerce; the term navy now designates only such vessels as are built and maintained specifically for war. There have been three major devel...

commerce, in economics

(Encyclopedia)commerce, traffic in goods, usually thought of as trade between states or nations. Engaged in by all peoples from the earliest times, it has been carried on in some areas and by some peoples more than...

aerodynamics

(Encyclopedia)aerodynamics, study of gases in motion. As the principal application of aerodynamics is the design of aircraft, air is the gas with which the science is most concerned. Although aerodynamics is primar...

trade

(Encyclopedia)trade, traffic in goods. Conducted by gift, barter, or sale, trade is one of the most widespread of all social institutions. The theory of commerce as imposed by the national state has varied from...

aviation

(Encyclopedia)aviation, operation of heavier-than-air aircraft and related activities. Aviation can be conveniently divided into military aviation, air transport, and general aviation. Military aviation includes al...

battery, electric

(Encyclopedia)CE5 Lead storage cell: At the lead-dioxide electrode, electrons from the circuit combine with lead dioxide and sulfuric acid to form lead sulfate and water. At the spongy-lead electrode, lead react...

iron

(Encyclopedia)iron, metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535℃; b.p. about 2,750℃; sp. gr. 7.87 at 20℃; valence +2, +3, +4, or +6. Iron is biologically s...