Meaning of AIR in English


Mixture of gases constituting the earth's atmosphere.

Some gases occur in steady concentrations. The most important are molecular nitrogen (N 2 ), 78% by volume, and molecular oxygen (O 2 ), 21%. Small amounts of argon (Ar; 1.9%), neon (Ne), helium (He), methane (CH 4 ), krypton (Kr), hydrogen (H 2 ), nitrous oxide (N 2 O), and xenon (Xe) are also present in almost constant proportions. Other gases occur in variable concentrations: water vapour (H 2 O), ozone (O 3 ), carbon dioxide (CO 2 ), sulfur dioxide (SO 2 ), and nitrogen dioxide (NO 2 ). Air also contains trace amounts of ammonia and hydrogen sulfide. The variable constituents are important for maintaining life. Water vapour is the source for all forms of precipitation and is an important absorber and emitter of infrared radiation. Carbon dioxide is necessary for photosynthesis and is also an important absorber and emitter of infrared radiation. Ozone in the stratosphere (see ozone layer ) is an effective absorber of ultraviolet radiation from the Sun but at ground-level is a corrosive pollutant and a major constituent of smog.


[c mediumvioletred] (as used in expressions)

air brake

air force

Air France

air mass

air pollution

air warfare

air conditioning

air cushion vehicle

compressed air

Eastern Air Lines Inc.

Royal Air Force

United States Air Force

{{link=United States Air Force Academy">United States Air Force Academy

Britannica English dictionary.      Английский словарь Британика.