Metric Units; Imperial Units; Only a few countries use them, including America; nerds use it for scientific measurements; 99% of the world uses them; Used for actually useful stuff, like cooking and measuring weight; 70 degrees is room temperature; Sweats producely at 70 degrees; you actually do math while doing unit conversions; unit conversions are boring, you just move the decimal place; examples of distance units: twip, poppyseed, barleycorn, Ramsden's chin, spindle; uses prefixes since they can't come up with original names for larger/smaller units