It's the root of many English words related to heat, including:
* Calorie: A unit of heat energy.
* Caloric: Relating to heat.
* Calorific: Producing heat.
* Calibrate: To adjust or standardize an instrument, often by using heat.
* Incandescent: Emitting light as a result of being heated.
* Kaleidoscope: Literally meaning "beautiful form of heat," referring to the changing patterns of light and color.
Interestingly, even the word "cold" has a connection to "calor" through the Latin word "frigus," which meant "cold" and was often used in contrast to "calor."