There's only one unit for each type of measurement in the SI. For example:
1)Regarding distance, in the SI there are meters and that's it; everything else is just a power of ten. On the other hand, the US Customary system has mils, inches, feet, yards, rods, furlongs, miles, nautical miles and leagues, with strange conversion factors between them all.
2)For volume, in the SI, there are liters and that's it; everything else is just a power of ten. On the other hand, the US Customary system has drams, teaspoons, tablespoons, ounces, gills, cups, pints, quarts, gallons, pecks, bushels, drums, beer barrels, liquid barrels, whiskey/kerosene barrels, oil barrels, cubic inches, cubic feet, cubic yards and I don't know of anyone who can remember the conversion factors for all those units! Oh--don't forget--a dry pint, quart, gallon or barrel is not the same thing as a fluid pint, quart, gallon or barrel, respectively.
