IOU stands for I owe you and we pronounce each letter separately. But how do we classify that construction"?

  • abbreviation: a shortened form of a word or phrase
  • acronym: an abbreviation formed from the initial letters of other words and pronounced as a word
  • Initialism: an abbreviation consisting of initial letters pronounced separately
  • back-formation: a word that is formed from an existing word which looks as though it is a derivative, typically by removal of a suffix

All definitions provided by Oxford Dictionaries Online

It can't be an abbreviation because there is no shortening, clipping or back-formation. Take for example phone which is an abbreviation of telephone, or edit which is a back-formation of editorship and editor. I would argue that abbreviations are words that have been shortened, a faster way of writing or saying something. Another example would be Prof for professor.

It can't be an acronym because we don't pronounce IOU as one word, whereas we do with NATO and RAM.

It can't be an initialism because if it was, it should be written as IOY (I Owe You)

Other examples that spring to mind is CU for see you and YRU for why are you, where initialism would dictate that the proper forms be SY and WAY.

How do linguists define this structure? Is there a more specific term than abbreviation?

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    I think you might want to use a broader definition of abbreviation. Wikipedia defines it as a shortening by any method. This could include phonetic. Commented Oct 23, 2014 at 6:45
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    great question ... you know, it's like an EARLY ("pre phone!")VERSION of "text spelling". Which is quite amazing.
    – Fattie
    Commented Oct 23, 2014 at 6:58
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    you know, it's rather like "OK" in a way. in a category of its own.
    – Fattie
    Commented Oct 23, 2014 at 7:20
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    Just wait till you get to QT for cutey, EZ for easy, or B̄Q̄ for barbecue: trust me, it’s all downhill from there.:) Especially once you include digits, so B4 for before, B9 for benign, 1K for wonky, W8 for wait, and much much worse, like somebody getting IR8 cause their partner was 2S9 & 4GO2 say 10Q after 4N6, losing out on a chance 2 4NK8 L8R. :) That’s Y 4N XL8Rs ❤ EZ words — & H8 2C ÞE words 2XL8 like μC4S.
    – tchrist
    Commented Oct 23, 2014 at 14:32
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    @Mari-LouA Too asinine.
    – tchrist
    Commented Oct 23, 2014 at 15:56

4 Answers 4


It could be characterized as a rebus

a riddle or puzzle made up of letters, pictures, or symbols whose names sound like the parts or syllables of a word or phrase [Merriam-Webster]

While a rebus often contains images, letters being used to represent syllables is common.

rebus card


In particular, the Encyclopaedia Britannica states

Literary rebuses use letters, numbers, musical notes, or specially placed words to make sentences. Complex rebuses combine pictures and letters. Rebuses may convey direct meanings, especially to inform or instruct illiterate people; or they may deliberately conceal meanings, to inform only the initiated or to puzzle and amuse.


A familiar English rebus is the debtor’s “IOU,” for “I owe you.”

If you wanted to be more precise in defining it, you could say alphabetic rebus.

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    Interesting idea, but aren't rebuses supposed to be solved? IOU doesn't need to be deciphered.
    – Mari-Lou A
    Commented Oct 23, 2014 at 12:02
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    Actually, for those unfamilar with the term (those who arrive in a space ship, or time travellers from the past, or maybe new English speakers) it does have to be puzzled out. You can't pronounce it phonetically. You kind of have to read it aloud, like an initialism, to get it.
    – bib
    Commented Oct 23, 2014 at 12:26
  • Not my downvote! I think the concept is novel (to me in any case). Could you find anything else about it? Linguistically speaking is it a used term?
    – Mari-Lou A
    Commented Oct 23, 2014 at 12:29
  • "Literary rebuses use letters, numbers, musical notes, or specially placed words to make sentences."
    – Mari-Lou A
    Commented Oct 23, 2014 at 13:53
  • Ian Rankin includes a very good example of such a thing in one of his Inspector Rebus novels. " (can't remember the first line).. A Q I C I 8 2 Q B 4 I P" Never knew that rebus was the word for them though. Commented Oct 23, 2014 at 14:16

I think it is a phonetic abbreviation in the sense that IOU represents the (phonetics) sound of “I Owe You”, not its proper initials, similar to CU for “see you”. (From The American Heritage® Dictionary of the English Language)

  • The act or product of shortening.
  • 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.

IOU: (from Investopedia)

  • An informal document that acknowledges a debt owed. IOU is an abbreviation, in phonetic terms, of "I owe you".
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    I think abbreviation can cover everything. I'm curious if there is a more specific term.
    – Mari-Lou A
    Commented Oct 23, 2014 at 6:54
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    I see your point..but in your question you say' It can't be an abbreviation'.
    – user66974
    Commented Oct 23, 2014 at 6:56
  • @medica I think it's closer to an initialism, each letter represents a word. But, until a few years ago I had never heard of clipping or back-formation, so maybe there's a term out there. I tend to think of abbreviations more like shortenings, but I could be wrong.
    – Mari-Lou A
    Commented Oct 23, 2014 at 7:36
  • @Mari-LouA You're right. Commented Oct 23, 2014 at 7:41
  • You know, I'm not convinced that "abbreviation" covers everything. If you asked your Mom what an abbreviation is, she'd probably think you mean "it uses initials". Almost anyone, I reckon, would say IOU is a "weird" abbreviation; indeed coz it is not initials-based.
    – Fattie
    Commented Oct 23, 2014 at 7:45

It is a gramogram or grammagram. https://en.wikipedia.org/wiki/Gramogram#Examples_of_sentences

A gramogram or grammagram or letteral word is a letter or group of letters which can be pronounced to form one or more words, as in "CU" for "See you". They are a subset of rebuses, and are commonly used as abbreviations.

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    I was asking myself how it was possible that no one posted this as an answer when I looked at the history of the Wikipedia article, and realised it was first created in 2016. Two years after I had originally posted my question.
    – Mari-Lou A
    Commented Oct 7, 2020 at 11:24

Initialism: an abbreviation consisting of the first letter or letters of words in a phrase, syllables or components of a word, or a combination of words and syllables and pronounced by spelling out the letters one by one rather than as a solid word. - AHDEL

There is also alphabetism (Farlex Trivia Dictionary): The expression of spoken sounds by an alphabet; the representation of the sounds of speech in consistent graphic form.

Initialisms (sometimes called alphabetisms) are formed from the initial letters of a string of words and are pronounced as a sequence of letters, e.g. BYOB, USA, DVD. Acronyms are formed from the initial letters or parts of words in a sequence, but have the distinction of being pronounceable words, e.g. RADAR, SCUBA.

Glottopedia defines alphabetisms as follows: an abbreviation that takes the first letter of each word of the base expression (like an acronym), and is pronounced by spelling out each letter.

But MW defines it as the use of letters as symbols; the representation of speech sounds by vowel and consonantal rather than syllabic signs. (IOU seems to fit that bill.)

Mindmap has subctegories of acronyms which are interesting to consider, including bacronym: refers to a word which seems like an acronym, but actually isn't, and states the difference between an acronym and an initialism is that an acronym forms a new word, while an initalism does not; you say "U.K." is an intialism for United Kindom: the periods are a dead-giveaway that's it's an intialism (but it's not an authoritative source).

Wikipedia, citing Homeland Security, calls it a pseudo-acronym, but the cited article doesn't list IOU.

I think it's a homoiousia of an alphabetism.

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    FYI is "for your information" and I have begun hearing people actually saying "eff wai/wye i" but said aloud neither -Y nor -F replace their corresponding word. On the contrary, -Y sounds like the word "why". Interestingly if you look up FYI many dictionaries list it as an abbreviation, and not an initialism. Which kinda bring us back to square one :))
    – Mari-Lou A
    Commented Oct 23, 2014 at 8:15
  • @Mari-LouA - indeed it does, and my head is spinning. See edit. Commented Oct 23, 2014 at 8:25
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    I now want a t-shirt with "I think it's a homoiousia of an alphabetism." on it.
    – skymningen
    Commented Oct 23, 2014 at 8:36
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    Hey, did you just say something despective about analphabetics? :)
    – tchrist
    Commented Oct 23, 2014 at 22:25

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