r   (TTS Sound)

The noun r has 4 senses

• roentgen, R -- (a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air)


• gas constant, universal gas constant, R -- ((physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole)


• R, r -- (the 18th letter of the Roman alphabet)


• radius, r -- (the length of a line segment between the center and circumference of a circle or sphere)