I would like to ask about a pronunciation rule that looks universal. There are (at least) 1201 words in English ending with "ous" and the majority of them are adjectives (http://www.morewords.com/ends-with/ous/). A random check shows that adjectives ending with "ous" are pronounced with "əs" at the end.

There are as well at least 68 words ending with "cious", like conscious, and apparently they are pronounced with "ʃəs" at the end (ˈkɒnʃəs).

Question. Do these two rules hold universally for adjectives? If yes then how such rules can be explained? (we know all that in English there are few pronunciation rules). Are there further rules of a similar nature?

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    There is no pronunciation rule in English that "holds universally". There shall always be exceptions, not to mention that the language is a living thing, so the "rules" do change. Commented Oct 3, 2015 at 11:17
  • Victor thank you for this comment. Could you please give me a simple example of a word ending with "cious" that is not pronounced with ʃəs at the end? If 99% of words ending with "ous" (let us exclude words like sous, i.e. plural of sou) are pronounced with əs at the end, I am already happy.
    – aglearner
    Commented Oct 3, 2015 at 11:27
  • A simple example? In other words, you're looking for the exception from the rule that you think is universal, yes? I don't have it handy, sorry. If I come across one in the future, I'll let you know. Commented Oct 3, 2015 at 11:47
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    Victor sure any exception will be the most welcomed, do share it with me if you stumble upon one. If there are no exceptions then the rule is indeed "universal" (if the proportion of exceptions is around 1% this is still not bad). Note that I slightly modified the question, since in reality I am only interested in adjectives ending with "ous" and "cious".
    – aglearner
    Commented Oct 3, 2015 at 12:21

2 Answers 2


The -cious rule holds for pretty much 100% of the time. Also, the -ous rule also holds for adjectives.


There are a couple suffixes/word endings in English that cause palatalization of the preceding consonant, if that consonant would otherwise be either /t, s, z/.

-ion, -ia, -io (/t/ only, and "patio" is an exception), -ious (this is what you're asking about), -ure, -ian (not all cases though, e.g. "Keynesian"),

These ones change the preceding consonant to a corresponding palato-alveolar consonant.


fusion /fjuʒən/

nature /neɪt͡ʃɚ/

pleasure /plɛʒɚ/

section /sɛkʃən/

combustion /kəmbʌst͡ʃən/

unconscious /ʌnkɒnʃəs/

This sort of sound shift occurs because of the preceding consonant assimilating with a palatal approximant /j/ (the Y consonant, the semivowel counterpart to /i/, which is now the long E sound) to result in the palato-alveolars.

Now let's deal with -ous. This suffix comes from Old French -ous, which is now French -eux. In turn this descends from the Latin -osus suffix.

Schwas often show up in unstressed syllables in English due to vowel reduction in unstressed positions, like this one.


I don't know if those pronunciations are universal, but I'll absolutely agree that if you're not sure of the pronunciation of a word that has one of those endings, those are by far the best guesses.

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