(physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole WordNet 3.0 & Open English WordNet

The molar gas constant is denoted by the symbol R or R. It is the molar equivalent to the Boltzmann constant, expressed in units of energy per temperature increment per amount of substance, rather than energy per temperature increment per particle. Wikipedia

Physical constant; the molar equivalent to the Boltzmann constant Wikidata

A universal constant, R, that appears in the ideal gas law, P V = n R T , derived from two fundamental constants, the Boltzmann constant and Avogadro's number, R = N A k . Wiktionary

Universal constant R. Wiktionary (translation)