##### Asked by: Portia Czernia

asked in category: General Last Updated: 27th March, 2020# What is the standard SI base unit of time?

**SI unit of time**. It is defined by taking the fixed numerical value of the cesium frequency Δν

_{Cs}, the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the

**unit**Hz, which is equal to s

^{-}

^{1}.

Also question is, what is meant by an SI base unit?

The **SI base units** are the standard **units** of measurement chosen for the seven **base** quantities chosen by the International System of Quantities: they are notably a basic set from which all other **SI units** can be derived.

Additionally, which is a base unit? A **base unit** (also referred to as a fundamental **unit**) is a **unit** adopted for measurement of a **base** quantity. The SI **units**, or Systeme International d'unites which consists of the metre, kilogram, second, ampere, Kelvin, mole and candela are **base units**.

Regarding this, how SI units are defined?

Medical **definitions** for **si units** A complete, coherent system of **units** used for scientific work, in which the fundamental quantities are length, time, electric current, temperature, mass, luminous intensity, and amount of substance.

What is the SI unit of speed?

**Units of speed** include: metres per second (symbol m s^{−}^{1} or m/s), the **SI** derived **unit**; kilometres per hour (symbol km/h); miles per hour (symbol mi/h or mph);