free energy -
(physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs; "energy can take a wide variety of forms"
physical phenomenon a natural phenomenon involving the physical properties of matter and energy
natural philosophy,
physics the science of matter and energy and their interactions; "his favorite subject was physics"
activation energy,
energy of activation the energy that an atomic system must acquire before a process (such as an emission or reaction) can occur; "catalysts are said to reduce the energy of activation during the transition phase of a reaction"
alternative energy energy derived from sources that do not use up natural resources or harm the environment
energy level,
energy state a definite stable energy that a physical system can have; used especially of the state of electrons in atoms or molecules; "according to quantum theory only certain energy levels are possible"
rest energy the energy equivalent to the mass of a particle at rest in an inertial frame of reference; equal to the rest mass times the square of the speed of light
work activity directed toward making or doing something; "she checked several points needing further work"
