What term means the energy an object has because of its rest mass?

The energy an object has because of its rest mass is called rest energy. It is given by Einstein’s famous equation E₀ = mc², where m is rest mass and c is the speed of light in a vacuum.

Rest energy is the energy associated with an object in its own rest frame, where its momentum is zero. Because the speed of light is squared, even a small amount of mass corresponds to a very large amount of energy: one kilogram has a rest-energy equivalent of roughly 9 × 10¹⁶ joules.

Albert Einstein introduced mass–energy equivalence in 1905. In nuclear reactions, a small reduction in the mass of the products can appear as kinetic energy, heat, radiation, or other forms. The total energy remains conserved even though rest mass may change.

Rest energy is not the same as kinetic energy, which depends on motion, or potential energy, which depends on position or configuration. Binding energy is energy associated with holding a system together and can contribute to its total mass, but it is not the definition of rest energy.