I know there is no strict rule on pronunciation of words in English but here my question is about the words which begin with 'con' and 'com', more than asking general rule.

When I look at the words begin with 'con' and 'com', I see mostly two patterns : One of them is schwa /ə/ sound and the other one is /o/ or /ɒ/ sound.But the second pronunciation can be pronounced slightly differently depending on dialect.

An example word for the first pronunciation is the word computer whose pronunciation is represented /kəmˈpjuː.tər/ in Cambridge Online Dictionaries.

An example for the second type of pronunciation for "co" could be the word contrast whose pronunciation is represented /ˈkɒn.trɑːst/ in Cambridge Online Dictionaries.

So my question is there any rule/pattern which can help us guess how to pronounce these words correctly?

I am not asking about the words like cool, come or coke. My question is about words like contract, combination, continue, combat.

  • I'm afraid not. I'll throw in cool, cozy and counter as hints that the simple combination co is absolutely arbitrary and no base for any rule that can be useful. There is the pronunciation of the c, which is constant, and the vowel sound o which may vary wildly. Especially the second one may be very interesting, but not in combination with a random consonant.
    – oerkelens
    Commented Feb 12, 2015 at 21:12
  • 2
    @oerkelens Erm, you're wrong about that one old bean. There is a very regular rule about the pronunciation of the con/com/cor/col prefix (it's the same prefix where the /n/ undergoes dealveolar assimilation according to the position of the following phoneme. If the word is stressed on the "con" prefix then the pronunctiation is with /kɒn/ otherwise it is /kn/! Not arbitrary in any way but completely regular and quite interesting! :-) Please retract your close-vote! UInless I'm missing something? Commented Feb 13, 2015 at 0:31
  • Hmmm. Interesting. How did my answer in 2014 get onto your question you asked in 2015? Time machine ... Commented Apr 4, 2016 at 14:26
  • @Araucaria there is another question which was merger with mine..and its date Feb 13, 2014.this could be the reason
    – Mrt
    Commented Apr 5, 2016 at 22:08
  • @Mrt Yes, I think so :-) Commented Apr 5, 2016 at 22:10

3 Answers 3


A very reliable rule of thumb for British English and General American is this:

  • If the syllable con is stressed it will take a full strong, vowel, and the first syllable will be: /kɒn/.

  • If the syllable is not stressed we will find a schwa, /ə/, or no vowel at all in the first syllable: either /kn/ or /kən/.

However, we should bear in mind that some regional varieties of English will have a full vowel in the first syllable of many of these words regardless of stress. So in Yorkshire English, for example, many speakers will say /kɒnˈstɪtʃʊənt/.

This morpheme 'con' occurs a lot in English. That last sound in 'con', /n/, is very unstable both because it is an alveolar sound and also because it is nasal. It tends to change according to the following consonant. We find this prefix with different final consonants in words like: collect, commemorate, correlate. These types of word also show the same variation in their first syllables depending on the stress:

  • colleague: /ˈkɒli:g/
  • collection: /ˈlekʃn/
  • compensate: /'kɒmpənseɪt/
  • computer: /km'pju:tə/
  • correlate: /ˈkɒrəleɪt/
  • corroborate: /'rɒbəreɪt/

Both words collection and corroborate could be said with no schwa at all, and just a syllabic consonant - but the transcription for this is tricky in terms of syllabification, so I have taken the easy route and used a schwa. Similarly, computer could equally be said with a schwa instead of a syllabic /m/.

[Transcription note: in line with the Original Poster's question I have used Southern Standard British English transcriptions].

  • +1 for being totally correct about Yorkshire English (though I have never heard it called that before!) using /kɑn/ almost exclusively. Commented Nov 14, 2014 at 13:47
  • There are also 3 exceptions for this rule where com- represents stressed /kʌm/ (in most accents of English): comfort, company, compass.
    – herisson
    Commented Nov 16, 2016 at 20:03
  • @suməlic Indeed. It's only a rule of thumb, but I've never been able to remember the exceptions. Thanks. Commented Nov 16, 2016 at 21:43

A useful guide is that /o/ sound tends to occur when the syllable is stressed and the schwa /ə/ sound is usually when the syllable is unstressed.

For example,

cóntrast and contrást

cóntrary and contráry

cómbat and combátant

cómbine harvester and combíne


According to SPE -- The Sound Pattern of English (which I think is right about this matter), when the primary stress is on the second syllable, a heavy first syllable gets a secondary stress, but a light first syllable remains stressless, except for Latinate prefixes (like "con-"), which remain stressless even though they are heavy.

By "heavy", I mean that a syllable has a tense vowel or ends in a consonant. (The SPE account does not make reference to syllables, but that's what it boils down to.)

So, e.g., "computer" has no stress on the first syllable, even though it's heavy ("com-" ends in a consonant) because "con-" is a Latinate prefix. Compare "pentagonal", with secondary stress on "pen". Or, also, "campaign", with secondary stress on "cam".

In the SPE analysis, whether primary stress will fall on the first syllable of a word, like your example "contrast" (noun), is a separate matter.

  • Just posted too. Snap!
    – Dan
    Commented Feb 12, 2015 at 21:28
  • Thank you this answer is like a candle in the dark pronunciation tunnel :)
    – Mrt
    Commented Feb 12, 2015 at 21:36

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