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Nomenclature for Powers of 10

(That is for 10X)

Symbol

X (Power of 10)

Prefix
     

y

-24

yocto

z

-21

zepto

a

-18

atto

f

-15

fermi

p

-12

pico

n

-9

nano

m

-6

micro (micrometer = micron)

m

-3

milli

c

-2

centi

d

-1

deci

-

0

No prefix

da

1

deka

h

2

hecto

k

3

kilo

M

6

mega

G

9

giga

T

12

tera

P

15

peta

E

18

exa

Z

21

zetta

Y

24

yotta

It is important to note that the kilogram is the only SI (International System of Units [Systeme International]) unit with a prefix as part of its name and symbol. Because multiple prefixes may not be used, in the case of the kilogram the prefix names of Table 5 are used with the unit name "gram" and the prefix symbols are used with the unit symbol "g." With this exception, any SI prefix may be used with any SI unit, including the degree Celsius and its symbol °C.

Example 1: 10-6 kg = 1 mg (one milligram), but not 10-6 kg = 1 µkg (one microkilogram)

Example 2: Consider the Washington Monument. We may write hW = 169 000 mm = 16 900 cm = 169 m = 0.169 km using the millimeter (SI prefix milli, symbol m), centimeter (SI prefix centi, symbol c), or kilometer (SI prefix kilo, symbol k).