Punctuation and Spacing with Abbreviations (from simple to not-so-simple)
- The abbreviation of a single word requires a period at the end.
- Mrs., Jr., Corp.
- Almost all small-letter abbreviations made up of single initials require a period after each initial but no space after each internal period.
- a.m., i.e., f.o.b.
- BUT: rpm, mpg, cpi, mph
- All-capital abbreviations made up of single initials normally require no period and no internal space.
- CBS, URL, AMA, AICPA, IRS, VIP, PSAT
- Exceptions: Retain the periods in geographic names (such as U.S.A.), academic degrees (such as B.A., M.S.), and a few miscellaneous expressions (such as A.D., B.C., P.O., and V.P.)
- If an abbreviation of two or more words consists of more than single initials, insert a period and a space after each element in the abbreviation.
- N. Mex., Lt. Col., Rt. Rev., loc. cit., nol. pros.
- One space should follow an abbreviation within a sentence unless another mark of punctuation follows immediately.
- You ought to talk to your CPA about the problem.
- Dr. Wilkins works in Washington, D.C., but lives in Bethesda.
- Please call tomorrow afternoon (before 5:30 p.m.).
- Two spaces follow an abbreviation at the end of a sentence that makes a statement. If the abbreviation ends with a period, that period also serves to mark the end of the sentence. If the abbreviation ends without a period, insert one to mark the end of the sentence and then leave two spaces.
- Helen returned from a trip to Washington, D.C. Next year ...
- We're flying over on Air France and coming back on KLM. If you ...
- No space should follow an abbreviation at the end of a question or an exclamation. The question mark or the exclamation point should come directly after the abbreviation.
- Did you see Phil being interviewed last night on CBS?
- Because of bad weather our flight didn't get in until 4 a.m.!
Source: The Gregg Reference Manual
