The following words are pronounced starting with an iks / igz:

  • extent [ɪkˈstent]
  • expect [ɪk'spekt]
  • exterminate [ɪk'stɜːmɪneɪt]
  • external [ɪkˈstɜːn(ə)l]
  • exhaust [ɪg'zɔːst]
  • examine [ɪg'zæmɪn]
  • exact [ɪɡˈzækt]

The following words are pronounced starting with an eks:

  • extant [ek'stænt]
  • extra ['ekstrə]
  • execute ['eksɪkjuːt]
  • exhale [eks'heɪl]
  • excellent [ˈeksələnt]
  • excavate [ˈekskəveɪt]

So, I have this question on my mind for a while: Is there a rule of thumb to determine whether the words starting with an ex must be pronounced with iks or eks?

  • 21
    I don't pronounce any "ex-" words as "iks-" (American English).
    – tenfour
    Commented Jan 12, 2012 at 14:40
  • Babylon English Dictionary. Commented Jan 12, 2012 at 14:57
  • 4
    @tenfour Nor do I (British and Canadian English). Commented Jan 12, 2012 at 18:15
  • @tenfour Nor me (Australian English). Commented Jan 12, 2012 at 22:28
  • 1
    FWIW, though M-W countenances final stress, I only have extant with initial stress.
    – nohat
    Commented Jul 14, 2015 at 1:03

8 Answers 8


First of all, this is British English, as the phonetic transcription [ɪk'stɜːmɪneɪt] makes clear ['kli:ə]. And this is a dialectal matter, so you should expect a lot of local and social variation on pronunciation, depending on what variety of English you speak.

The phonetics of the situation are very simple. English is a stress-timed language (as opposed to Romance languages, for instance, which are syllable-timed), which means that the natural unit of our speech is the stressed syllable, and the average time between stressed syllables is a constant in everyone's speech. We vary that rate for emphasis, but mostly it speeds up or slows down like music, rhythmically.

And in a stress-timed language with an unpredictable stress system, like English, there might well be two stressed syllables together with nothing between them (deFEND RUSSia), or there might be 3 or 4 unstressed syllables (dePENDing on whether the RUSSians do it) squeezed into that time. And when words get squeezed, I's get undotted and T's get uncrossed.

This is called Fast Speech Rules; it's a very popular part of phonological theory. And one of its important features in English is Unstressed Vowel Reduction. What this means is that, while American English has about a dozen phonemically distinct vowels (15 if you count diphthongs) in a stressed syllable, in an unstressed syllable very few can occur: predominantly /ə/ (with [ɨ] as a frequent allophone), but also /ɪ/.

Of the words cited by the original questioner, all but two follow the simple rule that unstressed /ɛ/ becomes /ɪ/. One is simply marked wrong -- exhale is stressed on the first syllable by most people; the contrast with inhale has overcome the tendency of bisyllabic verbs to be stressed on the second syllable.

And the other one -- extant -- has a primary stress on the second syllable, but there is also a secondary stress on the first syllable. English has at least three stress levels, and secondary stress (marked with a ˌ low apostrophe in the first syllable of words like rotational /ˌro'teʃənəl/) is common in long words. The dictionary these were taken from may not have marked secondary stress (many don't), or it may have been misplaced in transcription, but a native speaker would automatically give any unreduced initial /ɛ/ a secondary stress, so it's there whether it's marked or not.

  • 1
    FWIW, I (a British English speaker) pronounce exhale with the stress on the second syllable, and extant with the stress on the first. Commented Jan 23, 2012 at 11:34
  • 1
    ++1 great idea and link about stress-timed language Commented Feb 5, 2012 at 9:07
  • It’s not correct to say that the Romance languages are syllable-timed. Portuguese isn’t, for example. It’s just as much a stress-timed language as English is. Second, one does not require secondary stress to analyse English, and this is done with decreasing frequency. All that is required is to admit that vowels do not have to reduce just because they aren’t stressed. You have no need to go inventing stresses that are not even there. The OED3 gives your rotational example as Brit. /rə(ʊ)ˈteɪʃn̩(ə)l/, /rə(ʊ)ˈteɪʃən(ə)l/, U.S. /roʊˈteɪʃ(ə)n(ə)l/. Notice, no phantom stresses needed.
    – tchrist
    Commented Feb 19, 2012 at 20:08
  • 3
    Stress marking varies among linguists, as do opinions about the number of stress levels that are "required". And stress usage varies widely among speakers. If one followed your theory, then one would be required to account for the actual reduced vowels in English words by some other means (which you do not specify). All grammars leak, as Sapir put it. Commented Feb 19, 2012 at 23:51
  • 2
    I don't really see the need for mentioning stress vs. syllable timing (nor, especially, for making it sound like it’s a binary opposition)—vowel reductions in unstressed syllables are perfectly common even in languages like Estonian or Catalan, both of which score quite far towards the syllable-timed end of the PVI scale. Commented Aug 29, 2014 at 16:35

In English, vowels are often reduced in unstressed syllables, in this case meaning that [e] tends to become [ɪ]. This is what is going on here.

If the first syllable is stressed, it's eks. If the second syllable is stressed, it may be iks. I don't pronounce the first syllable of extant and expanse differently (both iks). So the only exception for me appears to be exhale, which I pronounce with more secondary stress on the first syllable than any of the iks words.

Look at the word extract. The stress changes depending on whether it is a noun or a verb, and so does the pronunciation of the first syllable.

And looking at the Merriam-Webster dictionary, some people pronounce extant with the accent on the first syllable; this is probably related to its being an exception.

  • This is it. When pronouncing the unstressed syllable, e shifts to ɪ. This is how we automatically and unconsciously create the sound of an unstressed e.
    – MetaEd
    Commented Jan 12, 2012 at 15:11
  • +1 for pinpointing what is unconsciously done when pronouncing these words. Your explanation applies wonderfully when there are two "e" letters in the same word, which are pronounced differently because the one is stressed and the other is not.
    – Irene
    Commented Jan 12, 2012 at 17:00

In my version of English, "exact" and "exhale" have the same vowel at the start of the word. But the phenomenon you describe isn't limited to "ex-", people pronounce "en-" in different ways too. I have a friend who says "injin" for "engine", and some people say "onvelope" for "envelope". In short: I think you can pronounce them "eks" all the time and it's probably not wrong.


I believe the phonological rule may work like this:

  • If the syllable ex- is stressed, the vowel is pronounced /ɛ/ (as in best); otherwise it can be (but is not necessarily) reduced to /ɪ/ (as the i in ignore). I think this applies to other first syllables with e/i sounds too. Whether or not the /ɛ/ is reduced probably depends on the speaker, dialect, etc.
  • If the syllable ex- is stressed or if what follows is a voiceless consonant, it is pronounced /-ks-/; otherwise, it is /-gz-/. A voiceless consonant is one that does not involve vibration of the larynx, where the the vocal cords are; this includes f, s, sh, voiceless th (voiceless fricatives; the voiceless th is found in thick), and k, p, t (voiceless stops/occlusives).
  • 4
    I'd never thought about it before, but I (SE UK) normally say ixact and extra, and it certainly seems to me I'm applying this rule. I can and do sometimes say exact, but I think that's usually only if I want to place stress on the whole word - and even then I doubt I do it very often. Commented Jan 12, 2012 at 18:58

There have been good answers already, but let me add some ideas:
1) first a quote from the book English Words

In some instances, [s]-->[z]: example, executive, exude. It is not just [s] gets voiced: [ks]-->[gz].
Often, the motivation for voicing is the absence of stress in the first syllable which weakens the strongly consonantal voiceless [k] to [g] which then spreads its voicing towards to [s]. The pattern is familiar from pairs such as Alex [ks] but Alexander [gz]. Voicing of [ks] to [gz] is restricted to cases in which the cluster is to the left of a vowel or a silent "ʌ": exaggerate, exaltation, exhaust...
However, if ex is stressed, [ks] may or may not be voiced: exercise, exile, exit, exodus. With some words in this group [ks], [gz] are acceptable: exhume, exile, existentialist, exit, etc.

2) indeed, perusing through Cambridge English Pronunciation Dictionary, one may notice that same word might start with any combination of -ek, -ik, -eg, or -ig (some, such as example or exude, have all of them)
3) recently I opened a pronunciation book of my non-English first language and I saw that some words are supposed to start with -eks while others with -egz . That surprised me since I always have used -eks. Therefore perhaps we shouldn't worry too much about this matter.


My guide to this is: If there is a vowel on each side of the x (example, exempt, examination, etc.) or if there is a vowel sound (exhaust, exhume, etc.), then the sound is "igs".

If the x is followed by a consonant (extend, extreme, expose, etc.), then the pronunciation is "iks".

  • In the first case the sound is most certainly not "igs". In fact you probably could't pronounce it like that even if you tried. You will end up pronouncing it "igz" every single time.
    – RegDwigнt
    Commented Aug 17, 2013 at 15:03
  • I was thinking that this sort of anticipatory assimilation in which the voicing from the vowel following the ks makes the gz, also applies when the following sound is a voiced consonant, but it turns out there are too few examples of those to get a good feel for it: ex-directory, exgenerated, exgurgitation, ex-meridian, ex-vaccine, ex-votive, and ex-voto were all I found.
    – tchrist
    Commented Aug 17, 2013 at 15:03

I can’t imagine anyone who isn’t part of the pin–pen merger ever pronouncing ex- as /iks/. It’s always either /ɛks/ or /ɛgz/ in my dialect, meaning that that /ɛ/ never reduces to [ɪ], [ɨ], [ᵻ], or [ə] for me — but YDMV (Yᴏᴜʀ Dɪᴀʟᴇᴄᴛ Mᴀʏ Vᴀʀʏ).

  • 2
    The pin-pen merger only merges these vowels before nasal consonants, like /m/ and /n/. Commented Jan 12, 2012 at 15:15
  • @PeterShor Ah, that makes sense. I still don’t reduce them that I’m myself aware of. But my diction is probably not relaxed enough.
    – tchrist
    Commented Jan 12, 2012 at 15:23

So, I have this question on my mind for a while: Is there a rule of thumb to determine whether the words starting with an ex must be pronounced with iks or eks?

No. They are not normally, pronounced like that by English and other British people. They just start with an "eks" sound.

This may be a feature of a non-English and non-British, regional accent. Maybe an American accent or one of a non-English speaking part of the world. Where did you get the idea that those words are pronounced like that? Was it by learning a regional accent, maybe from one person in particular? I know that many non-English speakers who learn the language, have difficulty pronouncing the e sound in words like bed and extra.

If you have that difficulty, the best thing for you to do is practice pronouncing that sound as much as you can, as well as listening to English people pronouncing it. You can master it, if you try. That would be better than trying to change it into another sound "iks", which just sounds weird and odd to a native speaker.

  • 6
    Exhaust and excellent do not have their first syllables pronounced the same way in normal British English; the reason for this are discussed in other answers. Perhaps iks is a poor transliteration (another reason to brush up on IPA); but airily dismissing the fact because you haven't heard it is unhelpful. Commented Feb 25, 2013 at 20:52
  • Tim, I was not intending to dismiss anything. I was making the point, perhaps I was not clear enough in doing so, that the words in question are normally pronounced with the e sound that is also in the words bed and extra.
    – Tristan
    Commented Feb 25, 2013 at 21:40

Not the answer you're looking for? Browse other questions tagged or ask your own question.