In the past, the systems of units most commonly used were the **English**
and **metric**, the English system is based on a single standard, the metric is subdivided into two interrelated standards:
The **MKS **and The **CGS**

The__MKS system__ uses *Meters*, *Kilograms*, and *Seconds*, while the __CGS system__ uses *Centimeters*, *Grams*, and *Seconds*.
Unfortunately, the use of more than one system of units in a world, would introduce unnecessary complications to the basic understanding of any technical data. The need for a standard set of units to be adopted by all nations has become increasingly obvious. In 1960, the General Conference adopted a system called **Le Systeme International d'Unites** *(International System
of Units)*, which has the international abbreviation **SI**.
The *International Bureau of Weights and Measures* located at Sevres, France, has been the host for the General Conference of Weights and Measures, attended by representatives from all nations of the world. Since then, SI has been adopted by the *Institute of Electrical and Electronic Engineers*, Inc. (IEEE) in 1965 and by the United States of America Standards Institute in 1967 as a standard for all scientific and engineering literature.

#### Meter

The **meter** was originally defined in 1790 to be 1/10,000,000 the
distance between the equator and either pole at sea level, a length preserved
on a platinum-iridium bar at the International Bureau of Weights and Measures at Sevres, France.
#### Kilogram

This standard is preserved in the form of a platinum-iridium cylinder in Sevres.
#### Second

The **second **was originally defined as 1/86,400 of the mean solar
day. However, since Earth's rotation is slowing down by almost 1 second
every 10 years,
This table shows interrelation between different systems of units.

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