For an acronym that includes the word "of", do you capitalize its usage within the definition (or expansion) of the acronym

For example, in the follow sentence:

My coworker Steve suffers from Complete Avoidance of Work Syndrome (CAOWS).

Should of be written as Of?

  • @Monica: I think your deleted answer is quite good. The only thing I'd add is a few general rules from a style book (I'm quite sure that such rules exist). Nov 28, 2011 at 5:32
  • Is CAOWS an acronym, and if so, how do you pronounce it? Or is the question about initialisms in general?
    – Hugo
    Nov 28, 2011 at 6:38
  • @Cerberus, I deleted it because I realized I'd answered a question he hadn't asked (and hadn't answered his). He asked about the spelled-out form, not whether to capitalize it in the abbreviation. Nov 28, 2011 at 13:59
  • Thank you everyone for an interesting discussion of this question. It was very useful, and has increased my understanding. Nov 29, 2011 at 0:00

5 Answers 5


First, some definitions from the Chicago Manual of Style:

  • acronym refers to terms based on the initial letters of their various elements and read as single words (AIDS, laser, NASA, scuba);
  • initialism refers to terms read as a series of letters (AOL, NBA, XML);
  • contraction refers to abbreviations that include the first and last letters of the full word (Mr., amt.).

As for the capitalization of these constructs, CMS has these recommendations:

Initialisms tend to appear in all capital letters, even when they are not derived from proper nouns (HIV, VP, LCD). With frequent use, however, acronyms—especially those of five or more letters—will sometimes become lowercase (scuba); those that are derived from proper nouns retain an initial capital. Chicago generally prefers the all-capital form, unless the term is listed otherwise in Webster’s. [NAFTA (not Nafta)]

On the other hand, if the words in a spelled-out version of an acronym or initialism are not derived from proper nouns or do not themselves constitute a proper noun (as in the official name of an organization), they should generally be lowercased, even when they appear alongside the abbreviated form. [transmission-control protocol/Internet protocol (TCP/IP)]

So, whether CAOWS is:

  • an acronym, pronounced cows
  • an initialism, pronounced "SEE-AY-OH-DUBYA-ESS"

the Chicago Manual, at least, would recommend you write:

My coworker Steve suffers from Complete Avoidance of Work Syndrome (CAOWS).

Note that in Nathan's comment, it's necessary to lowercase DoS (an acronym for denial-of-service) to disambiguate it from DOS (an acronym for disk operating system). I don't think CAOWS has any such problem.

  • Note that 'First, some definitions from the Chicago Manual of Style' may be taken to entail 'Here are the only and unchallengeably correct definitions of some terms'. This is not the case. 'First, here is how CMOS defines various terms ...' is more felicitous. Mar 29, 2020 at 14:36
  • It should be all lower case, not just the "of", because diseases and syndromes are not proper nouns: "... suffers from complete avoidance of work syndrome (CAOWS)". I was a bit surprised to see you quote the rule that explains this, complete with the TCP/IP example, and then you didn't follow it yourself! May 11, 2020 at 10:22

I wouldn't capitalize the o in "of".

Here's a well known example.


Test of English as a Foreign Language.

Typically, prepositions and articles should not be capitalized.

For a comprehensive capitalization rule list, see here.


If CAOWS were your acronym, then you would capitalize the O in "Of". If we use WINE as an example (Wine Is Not an Emulator), the "I" in "Is" is capitalized, but not the "a" in "an".

  • 3
    "is" is a verb and should be capitalized while "of" is a preposition and should not be capitalized, according to the general capitalization rules.
    – Terry Li
    Nov 28, 2011 at 5:39
  • Well, in sticking with computer industry acronyms, a DoS is a Denial-of-Service, whereas a DOS is a Disk Operating System. In the case of "Complete Avoidance of Work Syndrome", I'd be writing the acronym as CAoWS.
    – Nathan
    Nov 28, 2011 at 6:16
  • 2
    You are right. I assume OP wanted to know if the o in "of" should be capitalized or not in the expansion rather than how to format the acronym. It's good to know we can have lower cases in acronyms though. Thanks Nathan :)
    – Terry Li
    Nov 28, 2011 at 6:25

When writing out an acronym or initialism you do not capitalize the letter "o". As mentioned already, TOEFL is a good example of this as it is written out as Test of English as a Foreign Language (Cambridge University Press, About.com).

Note that the use of the letter "o" in the actual acronym or initialism is far more flexible and can be divided into three categories:

  1. The "o" is consistently capitalized, as is done in TOEFL.
  2. The "o" is omitted, as in ASEAN (The Association of Southeast Asian Nations).
  3. The "o" is printed in upper or lower case. For example, both LoA and LOA are common initialisms for Letter of Approval.

I follow a much simpler method. When you write out the full form and then include the acronym or abbreviation in parentheses, follow the general rule of capitalization in the full form. When the acronym or abbreviation is given first and then explained in full form, capitalize every word that has a representation in the acronym/ abbreviation.

Test of English as a Foreign Language (TOEFL)
TOEFL, Test Of English as a Foreign Language

I have had no problems with this so far.

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