The SI base units are:

*To do: merge Standards and Units with this. Incorporate operational definitions of units.*

Physical quantity | Symbol | Name of SI base unit | Symbol for SI unit |
---|---|---|---|

length | l | metre | m |

mass | m | kilogram | kg |

time | t | second | s |

electric current | I | ampere | A |

thermodynamic temperature | T | kelvin | K |

amount of substance | n | mole | mol |

luminous intensity | I_{v} | candela | cd |

All other physical units can be derived from these seven SI base units.

The SI prefixes are applied to abbreviate long numbers.