Metric Prefixes: From Nano to Mega

Read measurement terms quickly by decoding their Greek and Latin size prefixes.

Metric prefixes tell you exactly how large or small a unit is, and each one has an origin you can remember. Kilo- means one thousand, from Greek khilioi. Mega- means one million, from Greek megas, 'great. ' Centi- means one hundredth, from Latin centum, 'hundred. ' Milli- means one thousandth, from Latin mille, 'thousand. ' Micro- means one millionth, from Greek mikros, 'small. ' Nano- means one billionth, from Greek nanos, 'dwarf.

' A useful historical pattern: the original metric system used Greek prefixes for multiples (deca, hecto, kilo) and Latin prefixes for fractions (deci, centi, milli). Worked example: 'The cell membrane is about 8 nanometers thick, while the cell is about 20 micrometers wide. ' A nanometer is a thousand times smaller than a micrometer, so the membrane is a tiny fraction of the cell's width. Decoding the prefixes lets you compare sizes before doing any math.

• 1Kilo = thousand; mega = million.
• 2Centi = hundredth; milli = thousandth.
• 3Micro = millionth; nano = billionth.