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nitrogen

(Encyclopedia)nitrogen nīˈtrəjən [key], gaseous chemical element; symbol N; at. no. 7; interval in which at. wt. ranges 14.00643–14.00728; m.p. −209.86℃; b.p. −195.8℃; density 1.25 grams per liter at ...

motion picture photography

(Encyclopedia)motion picture photography or cinematography, photographic arts and techniques involved in making motion pictures. See also photography, still. Cinematography developed as a separate craft ve...

jet propulsion

(Encyclopedia)CE5 Types of jet engines: In the propeller-driven turbine a stream of high-velocity gases provides the power to drive the turbine and turn the propeller. In the jet-driven turbine the stream of gas...

chemical equation

(Encyclopedia)chemical equation, group of symbols representing a chemical reaction. There are a number of other symbols used in chemical equations. A symbol written above or below the reaction arrow indicates spe...

rain

(Encyclopedia)rain, precipitation in liquid form. It consists of drops of water falling from clouds; if the drops are very small, they are collectively termed drizzle. Rain plays a key role in the hydrologic, or wa...

protein

(Encyclopedia)protein, any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellu...

reproductive system

(Encyclopedia)CE5 Reproductive system reproductive system, in animals, the anatomical organs concerned with production of offspring. In humans and other mammals the female reproductive system produces the femal...

space shuttle

(Encyclopedia)space shuttle, reusable U.S. space vehicle (1981–2011). Developed by the National Aeronautics and Space Administration (NASA) and officially known as the Space Transportation System (STS), it was th...

gem, ornamental mineral or organic substance

(Encyclopedia)gem, commonly, a mineral or organic substance, cut and polished and used as an ornament. Gems also are used as seals (items of assurance) and as talismans (good-luck charms). For birthstones, see mont...

flight

(Encyclopedia)CE5 Aircraft motions and control surfaces: Yaw, or motion to the left or right, is controlled by the rudder. Pitch, or climbing or dropping, is controlled by the elevators, which move in the same d...