The following outline is provided as an overview of and topical guide to energy:
Energy – in physics, this is an indirectly observed quantity often understood as the ability of a physical system to do work on other physical systems.[1][2] Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert force (a pull or a push) against an object that is moving along a definite path of certain length.