R
n 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 [syn: 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 [syn: gas constant, universal
gas constant]
3: the 18th letter of the Roman alphabet
4: the length of a line segment between the center and
circumference of a circle or sphere [syn: radius]