The pica is a unit of length in the field of typography and uses the symbol pc.
There are 12 points in 1 pica. 1 pica represents approximately 1/6 of an inch.
Picas are expressed using numbers and a lower case p on software such as Adobe InDesign - for example 8p6 which would represent 8 picas and 6 points (or 8.5 picas).
The Pica is very useful in measuring and calculating the space needed to print letters and words on paper - for example when laying out books or magazine articles; the font lengths are quanitified by the number of characters per pica (cpp).
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.