**S**ystème

**I**nternational d'Unités) units are based on units of ten. Very large or very small numbers are easier to work with when you can replace any scientific notation with a name.

For example: the distance from City A to City B is 8.0 x 10^{3} meters. From the table, 10^{3} can be replaced with the prefix 'kilo'. Now the distance could be stated as 8.0 kilometers or shortened further to 8.0 km.

The distance from Earth to the Sun is approximately 150,000,000,000 meters. You could write this as 150 x 10^{9} m, 150 gigameters or 150 Gm.

The width of human hair runs on the order of 0.000005 meters. Rewrite this as 50 x 10^{-6}m, 50 micrometers, or 50 μm.

Metric or SI prefixes | |||

Prefix | symbol | x from 10^{x} | |

yotta | Y | 24 | 1,000,000,000,000,000,000,000,000 |

zetta | Z | 21 | 1,000,000,000,000,000,000,000 |

exa | E | 18 | 1,000,000,000,000,000,000 |

peta | P | 15 | 1,000,000,000,000,000 |

tera | T | 12 | 1,000,000,000,000 |

giga | G | 9 | 1,000,000,000 |

mega | M | 6 | 1,000,000 |

kilo | k | 3 | 1,000 |

hecto | h | 2 | 100 |

deca | da | 1 | 10 |

base | 0 | 1 | |

deci | d | -1 | 0.1 |

centi | c | -2 | 0.01 |

milli | m | -3 | 0.001 |

micro | μ | -6 | 0.000001 |

nano | n | -9 | 0.000000001 |

pico | p | -12 | 0.000000000001 |

femto | f | -15 | 0.000000000000001 |

atto | a | -18 | 0.000000000000000001 |

zepto | z | -21 | 0.000000000000000000001 |

yocto | y | -24 | 0.000000000000000000000001 |