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
n (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
n the 18th letter of the Roman alphabet
n the length of a line segment between the center and circumference of a circle or sphere
abbr. 和的平方根（root-sum square）；[拉]英国皇家学会会员（Regiae Societatis Socius, 等于fellow of the royal society）