Name | Symbol | Measure | Definition |

Meter | **m** | Length | The unit of length is equal to the length of the path traveled by light in a vacuum during the time interval of 1/299,792,458 of a second. |

Kilogram | **kg** | mass | The unit of mass is equal to the mass of the international prototype kilogram (a platinum-iridium cylinder) kept at the Bureau International des Poids et Mesures (BIPM), Sèvres, Paris (1st CGPM (1889), CR 34-38). Note that the kilogram is the only *base unit* with a prefix. |

Second | **s** | Time | The unit of time is the duration of exactly 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levelsground state of the cesium-133 atom at a temperature of 0 K. |

Ampere | **A** | Electrical Current | The unit of electrical current is the constant current which, if maintained in two straight parallel conductors, of infinite length and negligible cross-section, placed 1 meter apart in a vacuum, would produce a force between these conductors equal to 2 * 10 ^{− 7} newtons per meter of length. |

Kelvin | **K** | Thermodynamic Temperature | The unit of thermodynamic temperature (or absolute temperature) is the fraction 1/273.16 (exactly) of the thermodynamic temperature at the triple point of water. |

Mole | **mol** | Quantity of Matter (mass/mass) | A mole is the quantity of substance that contains the same number of elementary entities (atoms, molecules, ions, electrons or particles, depending on the substance) as there are atoms in 0.012 kilograms of pure carbon-12; this number (N_{A}) is approximately equal to 6.0221415(10) * 10^{23} mol^{-1} (2002 CODATA). |

Candela | **cd** | Luminous Intensity | The unit of luminous intensity is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 * 10^{12} hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. |