noun (n)

• a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air(noun.quantity)

  Synonym:
  roentgen
  

  source: wordnet30
• (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole(noun.quantity)

  Synonym:
  gas constant, universal gas constant
  

  source: wordnet30
• the 18th letter of the Roman alphabet(noun.communication)

  source: wordnet30
• the length of a line segment between the center and circumference of a circle or sphere(noun.attribute)

  Synonym:
  radius
  

  source: wordnet30