r meaning and definition

R noun

Definition of R (noun)

1. a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
   • synonyms: roentgen
2. (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
   • synonyms: gas constant, universal gas constant
3. the 18th letter of the Roman alphabet
4. the 18th letter of the Roman alphabet
5. the length of a line segment between the center and circumference of a circle or sphere
   • synonyms: radius