A force in nature which is recognized in various effects, but especially in the phenomena of fusion and evaporation, and which, as manifested in fire, the sun's rays, mechanical action, chemical combination, etc., becomes directly known to us through the sense of feeling. In its nature heat is a mode of motion, being in general a form of molecular disturbance or vibration. It was formerly supposed to be a subtile, imponderable fluid, to which was given the name caloric.
The sensation caused by the force or influence of heat when excessive, or above that which is normal to the human body; the bodily feeling experienced on exposure to fire, the sun's rays, etc.; the reverse of cold.
High temperature, as distinguished from low temperature, or cold; as, the heat of summer and the cold of winter; heat of the skin or body in fever, etc.