Q: Would you please address the disappearing period in print, from AD to MD to CC Sabathia. What is being saved by dropping the dot?
A. Many abbreviations have lost their dots lately in dictionaries and publications: RSVP, MD, USA, and scores of others.
This is an issue of style or convention, and such things change over the years—usually in the direction of simplicity. When in doubt, check your dictionary (and make sure it’s up to date).
If you’re writing for publication, follow the house style guide on whether to use points or not in specific abbreviations.
The New York Times, for example, generally uses points in abbreviations when the letters stand for separate words: F.C.C, I.B.M., N.R.A., J. C. Penney.
But the Times drops the periods in acronyms (abbreviations pronounced as words): NATO, AIDS, NASA.
The Guardian, on the other hand, doesn’t use points in abbreviations (or spaces between initials): BBC, US, mph, eg, etc, 4am, No 10, PJ O’Rourke, WH Smith.
As you can see, the conventions for using periods in abbreviations differ from publication to publication, dictionary to dictionary, style manual to style manual.
When you’re not writing for publication, be consistent. If you use dots with M.D. in one spot, don’t use a dotless MD in another.
We haven’t actually answered your question: What is being saved by dropping the dot?
Well, if you’re in a hurry, as so many of us are these days, every little dot counts.
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