Energy
the power that a body or system possesses of doing work; a term in physics. There is no manifestation of energy apart from matter. There are two main types of energy: Energy of motion (kinetic energy), and energy of position (potential energy). Currents of air or of water possess kinetic energy; a stone resting on the brow of a cliff, and water at the edge of a fall, possess potential energy. There is energy of visible motion and energy of position in visible arrangements of bodies, as in the bullet moving upward or downward, or at rest at its highest position. A bullet projected vertically upward possesses a great amount of energy. The higher it rises the less resistance can it overcome; and having reached the highest it can attain, it seems incapable of doing work, yet it will gradually acquire speed in the downward direction, and will finally (the resistance of the air being neglected) reach the ground with the same speed it had at first, and is thus capable of doing the same amount of work. When at its highest position and seemingly incapable of doing work, it really possesses energy as at first. A bent spring possesses potential energy.