The answer is Reduction. All three methods (convection, radiation, and conduction) are all ways of transferring heat. Convection is the transfer of heat by means of a medium such as air. Conduction is the transfer of heat from the contact of two surfaces at different temperatures. Radiation is the transfer of heat via electromagnetic waves.
Reduction is a chemical reaction that involves the gain of electrons. It is the opposite of oxidation which involves the loss of electrons.