### SI base unit - SI derived unit

The International System of Units (abbreviated SI) is the modern form of the metric system. It was established in 1960, and based on the meter-kilogram-second system. The units are divided into two classes—base units and derived units. The seven base units are represented different kinds of physical quantities.

Each SI unit is represented by a symbol, rather than an abbreviation. The use of unit symbols is regulated by precise rules. In the worldwide, in spite of using different language, however, these symbols are the same. "The SI is not static but evolves to match the world's increasingly demanding requirements for measurement."

### SI base unit

Name | Unit symbol | Quantity | Quantity symbol | Dimension symbol |
---|---|---|---|---|

metre | m | length | l (a lowercase L), x, r | L |

kilogram | kg | mass | m | M |

second | S | time | t | T |

ampere | A | electric current | I (an uppercase i) | I |

kelvin | K | thermodynamic temperature | T | Θ |

mole | mol | amount of substance | n | N |

candela | cd | luminous intensity | Iv (an uppercase i with lowercase non-italicized v subscript) | J |

### SI derived unit

Name | Symbol | Quantity | Equivalents |
---|---|---|---|

hertz | Hz | frequency | 1/s |

becquerel | Bq | radioactivity (decays per unit time) | 1/s |

siemens | S | electrical conductance | 1/Ω = A/V |

farad | F | electric capacitance | C/V |

lumen | lm | luminous flux | cd⋅sr |

weber | Wb | magnetic flux | J/A |

gray | Gy | absorbed dose (of ionizing radiation) | J/kg |

sievert | Sv | equivalent dose (of ionizing radiation) | J/kg |

watt | W | power, radiant flux | J/s = V⋅A |

degree Celsius | °C | temperature relative to 273.15 K | K |

newton | N | force, weight | kg⋅m/s^{2} |

lux | lx | illuminance | lm/m^{2} |

radian | rad | angle | m/m |

steradian | sr | solid angle | m^{2}/m^{2} |

katal | kat | catalytic activity | mol/s |

pascal | Pa | pressure, stress | N/m^{2} |

joule | J | energy, work, heat | N⋅m = C⋅V = W⋅s |

coulomb | C | electric charge or quantity of electricity | s⋅A |

ohm | Ω | electric resistanc impedance, reactance | V/A |

henry | H | inductance | V⋅s/A = Wb/A |

tesla | T | magnetic field strength | V⋅s/m2 = Wb/m2 = N/(A⋅m) |

volt | V | voltage, electrical potential difference, electromotive force | W/A = J/C |