The fermis is a unit of length in the non-SI metric system and uses the symbol fm.
One fermi is equal to 1×10−15m or 3.9370×10−14 in.
It is used to measure nuclear distances and was named after the Italian physicist Enrico Fermi (1901–1954). It has now been replaced with the SI-derived term femtometre.
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!