The total energy of a system can be subdivided and classified into potential energy, kinetic energy, or combinations of the two in various ways. Kinetic energy is determined by the See more

Classical mechanics
In classical mechanics, energy is a conceptually and mathematically useful property, as it is a See more

The fact that energy can be neither created nor destroyed is called the law of conservation of energy. In the form of the first law of thermodynamics, this states that a See more

The word energy derives from the Ancient Greek: ἐνέργεια, romanized: energeia, lit.'activity, operation', which possibly appears for the first time in the work of Aristotle in the 4th century BC. In contrast to the modern definition, energeia was a qualitative … See more

In 1843, James Prescott Joule independently discovered the mechanical equivalent in a series of experiments. The most famous of them used the "Joule apparatus": a … See more

Energy may be transformed between different forms at various efficiencies. Items that transform between these forms are called See more

Closed systems
Energy transfer can be considered for the special case of systems which are closed to transfers of matter. … See more