Acronyms That Are Plural

For acronyms, the rule is to use s without the apostrophe for a plural and the apostrophe-s for a singular possessive. Form plural possessive by adding an s-apostrophe. In the following example, assume I have many parts designated CTH and CTS, and only one CTM:

"Could you give me the engineering drawings for the CTHs? While you're at it, get me the CTSs' drawings, too. Don't forget that the CTM's total length depends on the size of the mandrel."

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As far as I know, the previously posted rule is true of all acronyms and also of other nonstandard word-like things such as numbers (imagine substituting part numbers 300, 400, and 500 in the given example).

Just because an acronym looks like a word, moreover, does not mean it takes the same ending as a noun in every case. Some acronyms are not nouns, but adjectives, depending on context. Some acronyms are adjectives all the time. Be careful.

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M.B.A's and Ph.D's are correct plural forms, according to <i>Chicago</i>.

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That should be "M.B.A.'s". Sorry

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I once read that in America, you use an apostrophe, but in England, it's just the s.

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Since I very fortunately do not work for the University of Chicago, a Chicago newspaper, or a Chicago-based corporation (anymore), I am free to use the construction that most of the country seems to prefer and which, likewise, seems to follow the most logical and understandable rule of clarity.

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"...and that seems to follow..."

(gropes for early morning coffee)

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It's never correct to use an apostrophe for plural acronyms, whether in the UK or the USA (or anywhere else).

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Sorry, I was mistaken. Speedwell2's examples, posted above on June 17, 2004, 12:35pm, are correct. I confused "acronyms" with "abbreviations."

Don't use an apostrophe for plural abbreviations that are more than 1 letter, whether in the UK or the USA (or anywhere else), unless the abbreviation has its own punctuation.

Examples:
We met 3 VIPs this year.
We hooded 12 Ph.D.'s at the most recent commencement ceremony.
I handed out IOUs to everyone at the race.

If the abbreviation is really an acronym, however, then you should only add a lowercase s to form the plural:

If we had more UNICEFs in the world, we might have less hunger.

What makes it an acronym? I think it's this: if one pronounces the letters, one after another, when it's spoken aloud, then it's an abbreviation. Example: we say, "In the UK" but it *sounds like* "in the you kay" because we are pronouncing each letter.

If one pronounces the acronym as if it were a word, then it's an acronym. Example: we say, "Four KARTS and thirteen NASCARs after his first race, Hollis McGumby was the winningest driver in the nation." Another example: If we had two NASDAQs, things would be different."

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In astronomy, one usually abbreviates Supernova as SN and the plural, Supernovae, as SNe.
Is this different because it's an abbreviation and not an acronym?
Or is it a special case of the above rule?
Or, most likely, is it plainly wrong?

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When following the write it out once rule, if the phrase is plural, e.g., Metropolitan Statistical Areas, should the abbreviation in parentheses be (MSA) or (MSAs)?

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