- meter (distance)
- kilogram (mass; related to weight)
- second (time)
- ampere (electric current)
- Kelvin (temperature)
- mole (amount of substance)
- candela (intensity of light)
Still other SI units—called SI derived units—are defined algebraically in terms of the
above fundamental units. All the base units are consistent with the metric system called
the MKS, or mks, system,which stands for meter, kilogram, and second. Another metric
system is the CGS, or cgs, system,which stands for centimeter, gram, and second.
What are some of the common metric/SI prefixes?
The common metric and SI prefixes have been around for a while, but some were only
recently added. In 1991, in order to apply standard units (SI units; see above) to a wide
range of phenomena (especially in the scientific world), the Nineteenth General Con-
ference on Weights and Measures lengthened the list to accommodate larger (and
smaller) metric numbers—with the list now reaching from yotta- to yocto-. The fol-
lowing lists the American system (the name for large numbers) and the corresponding
metric prefix and numerical equivalent (for comparison with prefixes and the power of
ten, see “Math Basics”):
Common Metric/SI Prefixes
American system metric prefix/symbol number
1 septillion yotta- / Y- 1024
1 sextillion zetta- / Z- 1021
1 quintillion exa- / E- 1018
1 quadrillion peta- / P- 1015 51MATHEMATICS THROUGHOUT HISTORY
What countries have not officially adopted the metric system?
T
o date, there are only three countries that have not officially adopted the met-
ric system: the United States, Liberia (western Africa), and Myanmar (former-
ly Burma, in Southeast Asia). All other countries—and the scientific world as a
whole—have either used the metric system for many years or have adopted the
measurement system in the past several decades. It’s a bit of historical irony to
note that the United States has hung on to such measurements as the foot, the
standard measurement originated by the English who now use metric.