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Noun: r  aa(r)
  1. The 18th letter of the Roman alphabet
    - R
     
  2. The length of a line segment between the centre and circumference of a circle or sphere
    - radius
Noun: R  aa(r)
  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
    "Early X-ray machines were calibrated in Rs";
    - roentgen, röntgen
     
  2. (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
    "The gas constant R is used in many thermodynamic calculations"; "The universal gas constant R is used in many thermodynamic calculations";
    - gas constant, universal gas constant

Derived forms: Rs, rs

Type of: alphabetic character, constant, length, letter, letter of the alphabet, radioactivity unit

Part of: diam, diameter, Latin alphabet, Roman alphabet

Encyclopedia: R,S-hydrobupropion