Conduction in thermotherapy is defined as

• A. Heat transfer by radiation
• B. Heat exchange between two materials with different temperatures
• C. Circulation of heated air
• D. Convective transfer within tissue

Answer: (B)

Conduction is heat transfer through direct contact between two materials with different temperatures. In thermotherapy, this means energy moves from the warmer surface (like a heated pad) into the cooler tissue by molecular interaction at the interface, warming the tissue beneath. This is distinct from radiation, which transfers heat without contact via electromagnetic waves, and from convection, which involves heat carried by moving air or fluid. Within tissue, conduction describes the direct transfer at the contact surface, whereas convection would require bulk movement of fluid (such as blood flow) to transport heat.