Quantity the change in which is equal to the sum of heat, \(q\), brought to the system and work, \(w\), performed on it, \(\Delta U=q+w\). Also called thermodynamic energy.
Green Book,2nd ed., p. 48 (https://www.cintegrado.com.br/site/documentos/green_book_2ed.pdf)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 976 (https://doi.org/10.1351/pac199668040957)