internal energy

of: a system

is: the energy arising from the kinetic energy of the system's constituents and the potential energy of their mutual interaction. [P7.3, P7.4, P7.5]

does not include: any contribution from the motion or position of the system as a whole. [P7.3]

changes: only as a result of heat transferred to the system or work done by (or on) the system, according to the first law of thermodynamics. Thus [P7.3, P7.4]

is: a function of state of the system. [P7.3, P7.4]