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Definition: Current in a fluid caused by uneven distribution of heat. For example, air on a part of the Earth's surface warmed by strong sunlight will be heated by contact with the ground and will expand and flow upward, creating a region of low pressure below it; cooler surrounding air will then flow in to this low pressure region. The air thus circulates by convection, creating winds.
Source: The American Heritage Science Dictionary. Boston: Houghton Mifflin, 2005. Credo Reference. Web. 08 August 2012.