Affixes

A thermometer (Latin ‑metrum, measure) measures temperature; a thermostat automatically regulates temperature; a thermocouple consists of two wires of different metals and also measures temperature, using the thermoelectric effect in which electricity is generated by a difference of temperatures; a thermoplastic substance becomes plastic on heating and hardens again on cooling; thermonuclear processes are nuclear reactions that occur only at very high temperatures; thermodynamics is the branch of physical science that deals with the relations between heat and other forms of energy; the adjective thermionic relates to electrons emitted from a substance at high temperatures. The usual adjective relating to heat is thermal.