Initialisms are pronounced as words and acronyms are spelt letters. However, some words sound the same, said and spelt.

e.g. Input Output can be abbreviated as IO. It can be spelt I-O or pronounced Io as in the moon/god. There is no way to tell the difference in how it is said or written.

Is a word which is pronounced the way it is spelt, an initialism, an acronym or both?

  • I'd say yes: the same way a word can be both a verb and a noun. So "IO" is a Homograph. – Joachim Sauer Nov 30 '11 at 9:08
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    I rarely, if ever, see input/output shortened to anything other than I/O. – Gnawme Nov 30 '11 at 18:22
  • Considering your OP and your comments, it seems that the title of your question should be edited to indicate your specific focus on IO. I'd rather you or a more senior ELU member do the edit, so for now I'm waiting for that or feedback on this comment. – sarah Dec 1 '11 at 1:33
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    If they both sound the same, how does it matter whether the person is "really" pronouncing the letters separately or the word? What does it even mean? – ShreevatsaR Dec 1 '11 at 8:47
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    The question has it backwards. An initialism is pronounced as individual letters. Examples: "USA", "BBC". An acronym is pronounced as a word using the language's orthography. Examples: "scuba", "radar". – MetaEd Oct 15 '12 at 4:37

I think you've misunderstood the difference between acronyms and initialisms. Something can be both, or just one and not the other.


a word formed from the initial letters or groups of letters of words in a set phrase or series of words, as Wac from Women's Army Corps, OPEC from Organization of Petroleum Exporting Countries, or loran from long-range navigation.


  1. a name or term formed from the initial letters of a group of words and pronounced as a separate word, as NATO for North Atlantic Treaty organization; an acronym.
  2. a set of initials representing a name, organization, or the like, with each letter pronounced separately, as FBI for Federal Bureau of Investigation.
  3. the practice of using initials or forming words from initials.

As you can see, WAC, OPEC and NATO are both acronyms and initialisms because they're a bunch of initials that you can pronounce as a word.

FBI on the other hand is a bunch of initials you cannot pronounce as a word; it's an initialism but not an acronym.

And finally, loran is pronounced as a word, but isn't only taken from initial letters; it's an acronym but not an initialism.

So for IO:

  • If you pronounce IO as a word (like Greek "io"), it's an acronym.
  • If you pronounce IO as letters I-O ("eye oh"), it's not an acronym.
  • In both cases, IO is an initialism.
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  • My question is; How would you tell is someone has pronounced something as I-O or io given they sound the same? Is this a question of intent? – Peter Lawrey Nov 30 '11 at 9:29
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    Ah, well the Greek word io is pronounced "ee-yoh" but sometimes "eye oh" in English. But IO is pronounced as "eye oh", and we have no idea whether the speaker is thinking of anglicised "io" or initials I-O, so I think it's fine to call it an acronym, but I probably wouldn't. – Hugo Nov 30 '11 at 9:43
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    @Wudang Yes, but the question here is a special case about a thing that usually sounds the same as a word ("io") and when spelled out (as "I. O."). – Hugo Nov 30 '11 at 11:51
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    Seems like we might have two related questions here: 1 Can something be an initialism and an acronym? 2. Is IO an initialism, or an acronym or both? – sarah Nov 30 '11 at 23:46
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    My understanding was that the two were mutually exclusive, as Grammar Girl says here: grammar.quickanddirtytips.com/acronyms-grammar.aspx However, either she and I were always wrong, or we were once right but are now wrong because what what once wrong has become right by virtue of its popularity. – sarah Nov 30 '11 at 23:52

It's an initialised (not initialized) acronym, or an acronymal initialism.

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    Initialized is a valid way of spelling initialised. – Hugo Nov 30 '11 at 13:54
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    Not to be taken seriously but... googlefight.com/… – Peter Lawrey Nov 30 '11 at 19:18
  • @Hugo, Also, PeterLawrey: I suggested initialised to distinguish from the existing word "initialized* [AmE], since my intention is a derivation from initialism. The downticks are based on this misunderstanding, I guess. – Kris Dec 1 '11 at 3:57

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