In mathematics, we find physical quantities such as length, mass, temperature, among others. These quantities are associated with certain quantities and a measurement standard called a unit of measurement or simply a unit. A magnitude is any physical property that can be expressed numerically.

A unit is a standardized quantity of a certain physical quantity. By standardized we mean that it takes its value from a pattern. Each physical quantity has a predefined (or basic) unit of measurement.

The metric system or International System of Units (SI) is the system most used at the measurement level. It consists of a set of seven fundamental (or basic) units, which express seven physical quantities; from these other units (known as derivatives) are determined.

**Fundamental Units**

Fundamental quantities | Fundamental unit | Symbol |

Length | meter | m |

Dough | kilogram | kg |

Time | second | s |

Electric current intensity | amp or ampere | A |

Temperature | Kelvin | K |

Amount of substance | mole | mole |

Luminous intensity | candle | cd |

**Derived units**

Derived quantities | Fundamental unit | Symbol |

Surface | square meter | m^{2} |

Volume | cubic meter | m^{3} |

Speed | meter per second | m / s |

Acceleration | meter per second squared | m / s^{2} |

Mass by volume | kilogram per cubic meter | kg / m^{3} |

Angular velocity | radian per second | rad / s |

Angular acceleration | radian per second squared | rad / s^{2} |

Frequency | hertz | Hz |

Force | Newton | N |

Pressure | pascal | Pa |

Energy, work, amount of heat | joule | J |

Power | watt | W |

Amount of electricity electric charge | coulomb | C |

Electric potential electromotive force | volt | V |

Electric resistance | ohm | W |

Electrical capacity | farad | F |

Magnetic flux | weber | Wb |

Magnetic induction | tesla | T |

Inductance | Henry | H |

**Supplementary Units**

Fundamental quantities | Fundamental unit | Symbol |

Plane angle | radian | rad |

Solid angle | steradian | sr |

**SI prefixes**

Unit symbols can be affected by prefixes that act as decimal multiples and submultiples. These prefixes are placed in front of the corresponding unit symbol with no space between.

Decimal multiples | Decimal Submultiples | ||||

Prefix | Symbol | Factor | Prefix | Symbol | Factor |

deca | da | 10^{1} | deci | d | 10^{-1} |

hecto | h | 10^{2} | centi | c | 10^{-2} |

kilo | k | 10^{3} | milli | m | 10^{-3} |

mega | M | 10^{6} | micro | μ | 10^{-6} |

jig | G | 10^{9} | nano | n | 10^{-9} |

tera | T | 10^{12} | pico | p | 10^{-12} |

peta | P | 10^{15} | femto | F | 10^{-15} |

exa | E | 10^{18} | atto | a | 10^{-18} |

zetta | Z | 10^{21} | zepto | z | 10^{-21} |

yotta | Y | 10^{24} | yocto | y | 10^{-24} |