On Tue, 26 Apr 2016 12:27:35 +1000, Monty wrote:
....

The metric system is an internationally agreed decimal system of
measurement. It was originally based on the mètre des Archives and the
kilogramme des Archives introduced by the First French Republic in
1799, but over the years the definitions of the metre and the kilogram
have been refined, and the metric system has been extended to
incorporate many more units. Although a number of variants of the
metric system emerged in the late nineteenth and early twentieth
centuries, the term is now often used as a synonym for the
"International System of Units"—the official system of measurement in
almost every country in the world.

The metric system has been officially sanctioned for use in the United
States since 1866, but the US remains the only industrialised country
that has not adopted the metric system as its official system of
measurement. Many sources also cite Liberia and Myanmar as the only
other countries not to have done so. Although the United Kingdom uses
the metric system for most administrative and trade purposes, Imperial
units are permitted or obligatory for some purposes, such as road
signs.
....

Excellent summary, let's hope the likes of Ken* read and understand
it!