Heat

[1] That which increases the internal energy of a body by changing the motion of the molecules. This causes a change in temperature, volume, or state of the body.
[2] Form of energy which acts on substances to raise their temperature; energy associated with random motion of molecules.
[3] The energy associated with the motion of atoms or molecules in solids, which can be transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation. All substances with temps above absolute zero contain heat
See also grass heat shield, manifold heat control valve