standard thermodynamic quantities
Values of thermodynamic functions in the @S05925@ characterized by a @S05921@, molality or @A00295@, but not by temperature. Standard quantities are denoted by adding the superscript \(^{\text{⦵}}\) or \(^{\unicode{x26ac}}\) to the symbol of the quantity.
Green Book, 2nd ed., p. 53 [Terms] [Book]
See also:
PAC, 1994, 66, 533. (Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994)) on page 536 [Terms] [Paper]