The transfer of heat caused by the movement of heated material.

In clouds, convection is the up-and-down movement of air caused by heat gradients or areas of different temperatures.

The transfer of heat through a fluid, air, and other gases and liquids: Such motion or convection is usually in the form of currents, in which the hotter, less dense material rises to be replaced below by cooler, denser substances.

Convection is the vertical movement of energy or mass by circulating currents.