The word coordinate has two vowels in it, that would ordinarily make the /u/ sound. Probably because of the word's etymology (Latin co- ‎(“together”) + ordinare ‎(“arrange”)) it is not pronounced as such but as two separate sounds.

Usually, the word for a pair of vowels would be a diphthong or a digraph, however, those words are reserved specifically for two vowels which make one syllable.

Two vowel sounds joined in one syllable to form one speech sound


Is there a specific linguistic term for a pair of vowels that, when pronounced, for two speech sounds?

  • I note that in the UK they often write coördinate, naïve, and so on to show ths type of pronunciation.
    – GEdgar
    Sep 24, 2016 at 13:05
  • @GEdgar Your bang on! I hadn't seen this before, but, as my answer details, it is used to differentiate between a diphthong and a diæresis. Sep 24, 2016 at 13:07
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    @GEdgar We don't often use a diaeresis, actually, and certainly vanishingly seldom on a letter other than i.
    – Andrew Leach
    Sep 24, 2016 at 13:20
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    @AndreLeach, yes the only times I can think of seeing it recently is on naïve Sep 24, 2016 at 13:24
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    @Airymouse It was a typo, should have been “you're bang on”, ‘bang’ being an intensifier here like ‘right on [the money]’. Sep 25, 2016 at 8:45

3 Answers 3


Adjacent vowels that are pronounced as separate syllables are said to be in hiatus:

A break between two vowels coming together but not in the same syllable, as in the ear and cooperate. (Oxford Dictionaries)

However, I don't know of any specific terms for the vowels themselves, or for the sequence of vowel letters.


It's not really a double vowel, in "coordinate," at least not like "wood."

The word used to be written "co-ordinate," meaning that the prefix, "co" was kept separate from the rest of the word.

"Modern" usage has blurred this distinction.

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    The spelling is arbitrary; the sound is a doubled vowel, separated by a semivowel - /kə'wordənet/. Sep 24, 2016 at 14:34
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    @JohnLawler A doubled vowel to me means the same vowel repeated. I don't recognise your transcription—I've always said and heard /koʊˡɔɹdɨnət/—but as I say it, the two o’s represent different vowels, and while the grapheme is doubled, the sound is not. It's a diphthong followed by a monophthong, just like go aboard or how indeed. Sep 25, 2016 at 8:51
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    @JanusBahsJacquet: Whether it's the same vowel is a dialectal matter. Phonetically, a diphthongized /o/ and a retroflexed /o/ can't be identical. However, in my American idiolect, /o/ and /ɔ/ are neutralized before /r/ (which is phonetically [ɹ] in my idiolect), so I represent them with the same phoneme for convenience, same as I represent [ɹ] by /r/. There does have to be a high back diphthong gesture between them, however, and I use /w/ for semivocalic /u/ or /ʊ/, when needed. But since all my tense vowels are diphthongized automatically, it's only necessary with a following vowel, as here. Sep 25, 2016 at 14:56
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    @JohnLawler Ah, I’ve become so inured to seeing phonetics in slashes on here that I didn’t realise you were talking phonemes. But if you’re saying the two vowels are phonemically the same and your tense vowels are automatically diphthongised (except where they merge with their lax counterparts), then surely the semivowel here is automatic and purely phonetic, and you’d more accurately have phonemic /koˈordɨnet/ in your notation. (Additionally, would tense and lax not merge before vowels too in most dialects, meaning you might as well write /kɔˈɔrdɨnet/?) Sep 25, 2016 at 15:25
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    One always uses the more common symbol to represent the phoneme, so even if I didn't want to emphasize the semivowel, I'd do it /ko'ordənet/. But, since phonemic representation is sui generis to a fault already, I prefer to use it to emphasize the points I want emphasized. That's the purpose of any orthography, imo. Sep 25, 2016 at 16:14

It appears I may have come to EL&U to hastily; the Wiktionary page for coordinate references an alternative spelling, coördinate which it explains is very rare, but helps explain its pronunciation.
The umlaut on the second 'o' is in this case called a diæresis, a mark that is becoming much rarer (as are most forms of accentuation in English).

(orthography) A diacritic ( ¨ ) placed over a vowel letter (especially the second of two consecutive ones) indicating that it is sounded separately, usually forming a distinct syllable, as in the English words naïve, Noël

As Wiktionary explains, the dieresis is becoming increasingly rare in US English typography, so the spelling coordinate predominates.

  • On page 503 of Garner’s Modern English Usage, Bryan Garner writes that “The phrase ✳increasingly less is a jarring oxymoron that would be better rendered less and less or decreasing...In fact, increasingly is a word that aspiring stylists might do well to jettison from their vocabulary—or at least use less and less.”
    – tchrist
    Sep 24, 2016 at 18:48
  • Yes, come to think of it, decreasingly would be the best replacement. Sep 24, 2016 at 19:49

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