r [ ɑ: ]

• 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

    同义词： roentgen

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

    同义词： gas constant universal gas constant

  • the 18th letter of the Roman alphabet

    同义词： letter r

  • the length of a line segment between the center and circumference of a circle or sphere

    同义词： radius

以上来源于: WordNet