[Mac Donald]

Originally Posted by chucker Er, yes, they're acronyms. You mean initialisms.

From Dictionary.com:

Abbreviation. . . .. 2. A shortened form of a word or phrase used chiefly in writing to represent the complete form, such as Mass. for Massachusetts or USMC for United States Marine Corps.

PDF for portable document format (again not sure it's format) just like USMC for United States Marine Corps.

An initialism is a type of abbreviation.

Initialism. . . . An abbreviation consisting of the first letter or letters of words in a phrase (for example, IRS for Internal Revenue Service), syllables or components of a word (TNT for trinitrotoluene), or a combination of words and syllables (ESP for extrasensory perception) and pronounced by spelling out the letters one by one rather than as a solid word.

PDF, CD, etc. are not acronyms.

Acronym. . . . A word formed from the initial letters of a name, such as WAC for Women's Army Corps, or by combining initial letters or parts of a series of words, such as radar for radio detecting and ranging.

(FYI: WAC is pronounced WACK, not W-A-C.)

From somewhere else on the internet, which ultimately agrees with chucker.

Some grammar books (not all) claim that apostrophes cannot be used in any plurals. This is considered an outdated view by many. In the 4 examples above, the apostrophes assist the reader and are acceptable. However, the plural of a normal-looking abbreviation should be shown by adding a small "s" without an apostrophe.

This is all about individual preference and usage -- the most important thing is to be consistent in an individual work of writing (I write for a living -- lawyering). The 1990s is considered by some to be correct, but I would use the 1990's, and that is MUCH more common.

Anyway, this is not exactly the most interesting argument. I guess no one else is having problems with PDF's in Camino on Mactels?????