R, n.
the 18th letter of the Roman alphabet
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R r
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(physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
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R gas constant universal gas constant
a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
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R roentgen
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