Wikipedia - Capacità termica (it) Wikipedia - Talk:Internal energy (en) heat capacity, $$C$$

https://doi.org/10.1351/goldbook.H02753
Heat brought to a system to increase its temperature divided by that temperature increase. At constant volume $$C_{V}=(\frac{\partial U}{\partial T})_{V}$$ at constant pressure $$C_{p}=(\frac{\partial H}{\partial T})_{p}$$, where $$U$$ is the @[email protected] and $$H$$ the @[email protected] of the system.
Sources:
Green Book, 2nd ed., p. 48 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 975 [Terms] [Paper]