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