energy

A measurable physical quantity, with dimensions mass times velocity squared, that is conserved for an isolated system.

Energy of motion is kinetic energy; energy of position is potential energy.
See energy conversion, internal energy, enthalpy.

Feynman, R. P., R. B. Leighton, and M. Sands 1963. The Feynman Lectures in Physics. Vol. I, . p. 4-2.