The metre (or meter; US spelling) is the SI base unit of length and uses the symbol m.
Originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole but was redefined in 1799 in terms of a prototyped metre bar (this bar was changed again in 1889).
In 1983 the current definition was adopted and it is now the most common unit in any property in the world and is used in thousands of formulae to describe countless characteristics.
Let's hear it for the metre!
The inch is a unit of length in the imperial unit system with the symbol in.
There are 12 inches in a foot and 3 feet in a yard. Therefore there are 36 inches in a yard. There are exactly 2.54 centimetres in an inch.
Borrowed from the Latin 'uncia' - the English word 'inch', the origination of the word came from the Old English word for 'ounce' which was related to the Roman phrase for "one twelfth".
The inch is still a commonly used unit in the UK, USA and Canada - and is also still used in the production of electronic equipment, still very evident in the measuring of monitor and screen sizing.