Standard for all Measurements - adopted 1866 by U.S.A.
LENGTH  -  METER
Distance Light travels in vacuum in 1/299,792,450 of second.
TIME  -  SECOND
Duration of 9,192,631,770 cycles of a specified radiation transition of cesium-133 atom.
MASS  -  KILOGRAM
Cylinder of platinum-iridium at National Bureau of Standards.
TEMPERATURE  -  KELVIN
1/273.16th triple thermodynamic temperature point of water (interface of solid, liquid, gas -
 .01 Celsius,  32.02 Fahrenheit).
ELECTRIC CURRENT  -  AMPERE
Current maintained in 2 parallel wires 1 meter apart (in free space), producing 2 x 10,000,000 newtons/meter.
LUMINOSITY  -  CANDELA
Intensity of 1/600,000 sq. m of cavity at platinum freezing temperature - 2,042 K.
AMOUNT  -  MOLE
Substance in elementary entities as atoms in .012 kg carbon-12.
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LINEAR
millimeter-mm, centimeter-cm, decimeter-dm, meter-m, dekameter-dam, hectometer-hm, kilometer-km
VOLUME
millilliters-ml, centilliter-cl, deciliter-dl, liter-l, dekaliter-dal, hectoliter-hl, kiloliter-kl
WEIGHT
milligram-mg, centigram-cg, decigram-dg, gram-g, dekagram-dag, hectogram-hg, kilogram-kg
1,000 kg = metric ton