Which of the following is not a form of energy?

Mass is considered a measure of the amount of matter in an object, and it does not represent energy in itself. The concept of energy encompasses various forms, such as kinetic energy (the energy of motion), chemical energy (stored in the bonds of chemical compounds), and electrical energy (associated with electric charge and currents). These forms of energy can be converted from one type to another and can perform work or produce heat. In contrast, mass does not have the same capacity to do work or transfer energy, making it fundamentally different from the other options listed.