Abbreviations – period or no period?

With complex and often contradictory rules, the English language can confound even the most careful practitioners.

One recent topic discussed in the writers’ corner at Goff & Howard was abbreviations. When are periods used, and when are they not?

Our most frequently used style guide, The Gregg Reference Manual, tells us that it depends on the situation. (Imagine that…)

Here are a few examples that we come across regularly:
• For the most part, uppercased abbreviations do not require periods. Examples include IRS, VIP, CEO, NFL, URL and CST. Favorite exceptions include academic degrees, like M.D. and B.S. And, according to at least one style guide (United States Government Printing Office Style Manual), CST should be c.s.t. We defer to The Gregg Reference Manual unless the situation dictates otherwise.
• Most lowercased abbreviations require periods. Examples include a.m., p.m., i.e. (that is to say), and e.g. (for example).
• When more than one letter is included per word in an abbreviation, use periods – Ph.D. and Lt. Col., for example.

Goff & Howard takes pride in getting the answers right on abbreviations and all kinds of other confounding grammar and usage questions. Then, on the most difficult occasions, The Gregg Reference Manual throws us a bone, telling us it’s okay to sometimes “manipulate the principles of style with intelligence and taste.*”

* William A. Sabin, The Gregg Reference Manual, Ninth Edition, Glencoe McGraw-Hill, New York, 2001, p. v.