More precise definition of a few metric (SI) base units:

  • s - second: One second is 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
  • m - meter/metre: One meter is the distance light travels in 1/299 792 458 of a second.
  • A - ampere: One ampere is the constant current which would produce a force of 2*10^-7 newton per meter of length when the currant is maintained in two straight parallel conductors of infinite length and neglectible circular cross section placed one meter apart in vacuum.
  • K - kelvin: The kelvin, unit of thermodynamic temperature, is the fraction of 1/237.16 of the thermodynamic temperature of the triple point of water.
  • kg - kilogram: A kg is equal to the mass of the international prototype of the kilogram. (A particular cylinder of platinum-iridium alloy that is preserved in a vault at Sevres, France.) (Duh!)
  • cd - candela: The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 * 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
  • mol - mole: The amount of a substance that contains as many elementary entities as there are carbon atoms in 0.012 kg of carbon 12

And so on... most of the others are derived from these.
  • Tabeller og formelsamling / Gyldendal norsk forlag AS 2001
  • University Physics / Young & Freedman / Addison-Wesley Publishing Company, Inc. 1996
(Thanks to Professor Pi for correcting some horrible errors)