From the passage provided, extract the two forms of energy transfer and list them in bullets.

The First Law of thermodynamics is a formulation of the law of conservation of energy, adapted for thermodynamic processes. A simple formulation is: "The total energy in a system remains constant, although it may be converted from one form to another." Another common phrasing is that "energy can neither be created nor destroyed" (in a "closed system"). While there are many subtleties and implications that may be more precisely captured in more complex formulations, this is the essential principle of the First Law.

It distinguishes in principle two forms of energy transfer: heat, and thermodynamic work, for a system of a constant amount of matter. The law also defines the internal energy of a system, an extensive property for taking account of the balance of energies in the system.

The two forms of energy transfer are:
- Heat
- Thermodynamic work