What does the abbreviation "BTU" signify?

The abbreviation "BTU" stands for British Thermal Unit. A BTU is a measure of heat energy and is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure. This unit is essential in various applications, particularly in heating and cooling, as it provides a standardized way to quantify thermal energy. Understanding BTUs is crucial for power engineers as it helps them assess the energy output of heating systems, air conditioning units, and other thermal processes.

The other options, while they contain terms related to thermal energy, do not accurately define what BTU represents in the context of energy measurement.