internal energy, \(U\)

Synonym: thermodynamic energy
Quantity the change in which is equal to the sum of heat, q, brought to the system and work, w, performed on it, ΔU = q + w. Also called thermodynamic energy.
Green Book, 2nd ed., p. 48 (
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 976 (