What term describes thermal energy that is in transition?

The term that describes thermal energy in transition is "heat." Heat refers specifically to the energy that is transferred between substances or systems due to a temperature difference. When two objects at different temperatures come into contact, thermal energy moves from the hotter object to the cooler one until thermal equilibrium is reached, which is the essence of heat transfer.

Calorimetry is a technique used to measure the amount of heat involved in chemical reactions or physical changes but does not itself describe the process of thermal energy moving. Temperature, on the other hand, is a measure of the average kinetic energy of the particles in a substance and does not inherently describe energy in transition. Thermal conduction is a process of heat transfer through a material without the movement of the material itself, and while it describes a mechanism of heat transfer, it does not define the energy itself that is transitioning. Therefore, "heat" is the most accurate term for energy in transition.