2010-10-13

Covering all our bases

Over the next few days, I intend to introduce you to some of the base units of the International System of Units (SI). Before I do, I'd like to spend some time on the prefix; a major component of SI units and a key advantage over other systems of measure.

A prefix is added to a "base unit" to indicate a multiple (or subdivision) of that unit. (We're already somewhat accustomed to this idea in computing.) The beauty of the prefix is that it represents a power of ten (e.g. 1, 10, 100, 1000, etc.).

(Some) Standard SI prefixes (Name [symbol] Factor = Number "cardinal/ordinal"):
micro- [μ] 10-6 .000001 "millionth"
* milli- [m] 10-3 .001 "thousandth"
* centi- [c] 10-2 .01 "hundredth"
deci- [d] 10-1 .1 "tenth"
100 1 "one"
deca- [da] 101 10 "ten"
hecto- [h] 102 100 "hundred"
* kilo- [k] 103 1 000 "thousand"
mega- [M] 106 1 000 000 "million"
giga- [G] 109 1 000 000 000 "billion"
tera- [T] 1012 1 000 000 000 "trillion"

You can find more information (and a better chart) in the SI prefix Wikipedia article.

Spend some time familiarizing yourself with the prefixes. I placed asterisks next to the ones I believe are the most common. Learn the relationships between the prefix and its base (e.g. 1000 units in a kilo-, 100 centi- in a unit, etc.). Since our number system is base 10, learning/counting multiples of ten comes naturally (literally, on our hands and feet).
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