I would like to know how to spell a word with two consecutive U's out loud—like "vacuum". Do we say vee, ay, see, double U or just U, U, em? I'm wondering because if we say "double U" it might be mistaken for the letter "W". But, in fact, the word "vacuum" is not written with a "W".

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    Note that using "double" to spell out a repeated letter (or number) appears to be a British (or, at least, non-American) habit. In my experience, if you say "double" in spelling out a word or number to Americans, they often get confused, and might well interpret "double ess" as 'ws' rather than 'ss'.
    – Colin Fine
    May 24 '16 at 11:02
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    Note also that the double u in "vacuum" has a somewhat similar but not identical sound to the double-u in "cwm" (a loan-word from Welsh), so there may be some (albeit very small) risk of spelling it "vacwm". May 24 '16 at 12:53
  • One could take a cue from NASA/etc and say 'zero-pressure' instead :-) May 24 '16 at 21:51
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    @ColinFine: That use of "double" definitely exists in the US, though I think it's less common here than just saying the letter twice.
    – ruakh
    May 25 '16 at 0:45

I have in fact heard (American) native speakers spell two consecutive U's out loud as "double U".

There is no rule. Language is something to have fun with, and there is a wee bit of fun in saying "double" and then the name of a doubled letter instead of saying the name of the letter twice in a row. When spelling out VACUUM, saying "double U" is ambiguous, and there is a wee bit of fun in choosing the ambiguous way to say it.

If you want to avoid ambiguity, of course, you can say "U U". The choice is yours.

However, there is less ambiguity than you might think. The name of the letter W has primary stress only on the first syllable: /'dʌb.l.ju/. When people say "double-X" where X is any letter, they usually fully stress both the first syllable of "double" and the name of the letter. For F, that would be /'dʌb.l.'ɛf/, not /'dʌb.l.ɛf/. For U, that would be /'dʌb.l.'ju/, not /'dʌb.l.ju/.

Also, rhythm is very important in English. Normally when people spell out a word, they give each letter the same amount of time and equal stress. When spelling out CAT, for example, people usually say /'si.'eɪ.'ti/, maintaining a steady beat so each syllable takes the same amount of time. When spelling out AWE, the time spent on each letter stays the same even though it takes three syllables to say the W: /'eɪ.'dʌb.l.ju.'i/; the three syllables of /'dʌb.l.ju/ are spoken quickly, totaling the same amount of time as /'eɪ/. When people indicate a doubled letter with the word "double", it usually makes rhythm irregular. Usually the time spent on the word "double" is a less than the time spent on each letter's name. Sometimes people squeeze "double" into the letter-name's time, or into twice the time of one letter-name, similar to a grace note in music.

But it's not a rule.

By the way, the letter W started as two consecutive U's; hence the name. Back then, U was written V; hence the shape.

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    Notably, the French name for the letter 'W' translates to "double-V". Not sure about other languages. May 24 '16 at 20:57
  • @Darrel Hoffman French is not the only one! I know of at least 6 other languages that do the same.
    – AndrejaKo
    May 24 '16 at 21:13

Your analysis is correct. A native speaker would realise the ambiguity and spell it out loud as:

Vee Aye See You You Em

We never say "Double-You" for anything but the letter "W".

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    Never? I'm a native English speaker, and I've said "double U" from time to time - but I wouldn't say it the same as the letter W. The letter W I say with emphasis only on the first syllable, DUB-uhl-you. Whereas "double U" would be enunciated more clearly with emphasis mainly on the U, like DUB-uhl YOU. (But more commonly I would spell it out your way.)
    – nnnnnn
    May 24 '16 at 11:40
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    @luxcem, do you spell 'FOOD' as "Eff two Oh Dee" ? That sounds weird.
    – Varun Nair
    May 24 '16 at 13:09
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    I (native AmE speaker) find this phonetic spelling confusing. "Aye" sounds like "I". For the letter A I would use something like "ay" or "eigh".
    – Era
    May 24 '16 at 14:00
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    I would also like to highlight that "Aye" is confusing. As a scotsman, "aye" is already a word and shares its pronunciation with the letter "I". May 24 '16 at 14:36
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    V-I-C-U-U-M? I thought it was vaccum.
    – Octopus
    May 24 '16 at 21:24

There is no inherent ambiguity because Double U (back-to-back letter u's) is pronounced differently from Double U (the letter W).

The letter w is pronounced as one three-syllable word with the stress on the first syllable. Listen here on Forvo. In addition–although not as important–in rapid speech, some speakers of English pronounce W as if it had no l, so dúbba-yu.

To refer to back-to-back u's, the native speaker will pronounce this as two words, with a slight pause between Double and U, and with stress on both words, double and u. In fact, to deliberately avoid ambiguity, they would slow down and make sure the addressee heard it as two words.

This would be true whether spelling V-A-C-Double U-M or some sequence as J-3-Double U-4-underline (J3UU4_) as in a password. One would not usually mistake this for J3W4_, because the W in that would be pronounced differently, as explained above. If the speaker or listener had any doubt, they could always ask for clarification. If there was extreme importance or noise interference they could use a phonetic alphabet.

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    In a real life situation where this was important, it would be much better to pronounce J3UU4 as "juliet three uniform uniform four", of course
    – alephzero
    May 24 '16 at 16:54
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    When describing how a word is spelled, saying "DOUBLE [pause] U" instead of "U U" kind of defeats the purpose of what one is saying, in my opinion. Why not eliminate ambiguity altogether (inherent or otherwise) instead of relying on subtle (to a non-native speaker, at least) pronunciation differences?
    – Michael J.
    May 24 '16 at 22:22
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    Don't forget that some of us pronounce W with two syllables, dubya ;)
    – ColleenV
    May 24 '16 at 22:30

You could also use the phonetic alphabet to spell it out too if you know it. This type of ambiguity was why these were developed.

In the NATO/ICAO Phonetic Alphabet:

Victor Alpha Charlie Uniform Uniform Mike

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    Using this alphabet could raise some eyebrows, especially if people are not used to spelling words like an air traffic controller, but in my opinion it's definitely worth it.
    – A. Darwin
    May 25 '16 at 15:19
  • @A.Darwin Anyone who has also served in the military would understand too. May 25 '16 at 16:15
  • Of course, I should have written "ATC and military or former military" (by the way I can't edit my comment anymore). However, I believe my point still stands: many people are not familiar with it, but when you hear a word spelled using the NATO/ICAO alphabet, you can't go wrong.
    – A. Darwin
    May 25 '16 at 16:21
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    The only time I get into trouble doing it is if I say "niner" to someone not used to the phonetic alphabet. They usually get there, but it definitely trips up their thinking. Otherwise, people seem to understand very quickly what I'm doing. May 25 '16 at 17:27
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    @T.J.Crowder I think even if folks don't know the NATO/ICAO alphabet, most are familiar with spelling alphabets (even if they just make them up as they go) C as-in-charlie O as-in-octopus double L as-in-lady double E as-in-evergreen N as-in-Nancy V as-in-Victor. ;)
    – ColleenV
    May 27 '16 at 14:15

When spelling something out loud, the intent is to be especially clear and unambiguous. To that end, even if you used the terminology "double" in general, you should avoid it in this case.

In fact, you may want to (or need to) use a phonetic word spelling in this situation too, so you actually spell out loud, "victor alpha charlie umbrella unicorn mary". Using two different words, though non-standard, helps convey the repetition within the message rather than the message fragment being repeated, which is another source of ambiguity.


why not "double U's" with a z sound at the end. or maybe : "two U's".

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    "The two what, mister Gambini?"
    – Stavr00
    May 24 '16 at 19:12

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