The long and the short of it

The format of abbreviations, in particular whether they end with a full stop, follows a fairly simple rule. Specifically, if the abbreviated word is truncated (the end is chopped off), then the abbreviation ends with a full stop (also called a period). Whereas, if the word is contracted (middle letters are removed), then there is no ending full stop.

For example, the abbreviation govt has no ending full stop because the word is contracted—that is, both the word and its abbreviation end with the same letter (government). And the abbreviation co. ends with a full stop because the word is truncated—that is, the word and its abbreviation end with different letters (company).

Here are a few more common abbreviations, some with and some without the ending full stop:

• std dev.

• max.

• regn

• approx.

• dept

• incl.

• fig. (plural figs)

But don’t confuse abbreviations with shortened words that have been adopted as words in their own right in the dictionary, such as phone (telephone), flu (influenza), blog (weblog), lab (laboratory), and ad (advertisement). When an abbreviation is adopted as a word, typically because it is in common use, it is spelled without punctuation (no full stop or apostrophe).

And just to keep you on your toes, there are different rules for other forms of shortening, including acronyms, initialisms, contractions, Latin abbreviations, and omitted letters. For example, acronyms and initialisms are formed without full stops (yes, even in the US), and the form of the indefinite article, “a” or “an”, that precedes an acronym or initialism depends on its pronunciation, not its spelling (a MASH but an MBA, a UFO but an UNSUB).

For a complete discussion, check out Formatting>Abbreviations, initialisms, and acronyms and related articles in the Doxical Style Guide for Miners and Geoscientists.