I've been in the belief that we shouldn't capitalize the prepositions in titles or abbreviations until I started working in a company, where most of the colleagues are American.

When they say "Out of office," they type "OOO" instead of "OoO," and "WFH" (for "Work from home") instead of "WfH."

Am I wrong, or are they wrong? Should I stick with my weird "OoO" or conform?

  • 2
    Acronyms are traditionally all uppercase or sometimes all lowercase, eventually.. YoU doN't mix. – tchrist Aug 10 '19 at 5:18
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    In Britain, the Court Of Protection is often written as an acronym "CoP". – Michael Harvey Aug 10 '19 at 9:14
  • I have found prepositions/determiners were sometimes lowercased or ignored completely. – marcellothearcane Aug 10 '19 at 13:56
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    There's nothing wrong with either OoO or OOO, but I'd say in general, it isn't a question of whether prepositions are capitalized in abbreviations, but whether they are included at all. In US government units, for instance, it's the FBI, not FBoI, and the NEA, not the NEftA, but it's always the DOJ and the LOC, not to mention SCOTUS. – choster Aug 10 '19 at 13:56

There is no "rule" that the letters making up initialisms must be all one case. In Britain, Transport for London is abbreviated to "TfL", and the Court of Protection can be either the "COP" or "CoP". Initialisms which are also acronyms, like scuba, laser, radar, etc, have become words in their own right. As you have found, individual organisations have their own conventions about capitalising, and you would be wise to adhere to them.


You have answered your own question: "Should I stick with my weird OoO?"

If a mixed-case initialism is weird, then why stick with it?

When handwriting such an abbreviation, it makes little difference. With the ubiquity of electronic communication, there is a difference: WFH takes four keystrokes ShiftWFH but using a lowercase letter in the middle takes five: ShiftW F ShiftH. Why make work?

As Michael Harvey observes, some organisations will have their own style. Transport for London not only uses a lowercase f but italicises it: TfL. And it's even like that on manhole covers.

Just do what's usual. OOO and WFH are perfectly normal and expected. If you're working somewhere where they're not, use what is.


Just follow suit, go with the flow, and copy what your bosses and peers do. Or you could laugh in the face of danger and ridicule, comfortably knowing a lowercase letter can stand for a preposition when it is flanked by two uppercase letters.

Terms of service also known as Terms of Use or Terms and Conditions

can be abbreviated as TOS or ToS, ToU or T&C (Wikipedia)

On Stack Exchange, the Code of Conduct is often shortened to CoC, which I would advise not to pronounce as one word in the company of strangers. Keep it as an initialism.

  • In aviation the angle of attack of an aircraft in flight is seen both as "AOA" and "AoA" in technical/official material. – Michael Harvey Aug 11 '19 at 12:17
  • Interesting, here COC stands for the oldest LGBT organisation. – JJJ Aug 13 '19 at 12:47

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