Usually -tion words, such as motion, education, and lotion, end with a -shn sound. But equation ends with a sound rhyming with vision.

Are there many more? What might some of them be? And if the pronunciation of equation is a rarity for words ending in -tion, why did that pronunciation for it arise? I'm asking this since I am not a native English speaker and discovered this exception accidentally.

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    Seems both versions of pronunciation are correct: -shn and -zhn. en.wiktionary.org/wiki/equation
    – Arsen Y.M.
    Commented Feb 20, 2015 at 20:12
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    A list would be very long indeed.
    – Centaurus
    Commented Feb 20, 2015 at 21:23
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    Voting to reopen. This is NOT a question suitable for ELL. Those who think it is should perhaps try giving an answer to it. As someone trained in both phonetics and comparative linguistics, I have no idea what the answer is—if you think this is something any English speaker can answer, I'd say think again. Commented Feb 21, 2015 at 9:12
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    @MAKZ: In an effort to encourage others to reopen this question, I have tried to make explicit the issue of greatest interest to EL&U participants—by adding the sentence "And if the pronunciation of equation is a rarity for words ending in -tion, why did that pronunciation for it arise?" to your original question. I hope that this will meet with your approval; if it doesn't, you can roll back to the earlier version of the question.
    – Sven Yargs
    Commented Feb 21, 2015 at 20:53
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    It might be just me, but I assume the standard algebra term equation (voiced "-zhn") refers to things like a=b+c and e=mc². When it comes to the more general context of one thing being equated with another (treated as "equal"), I'd be more than happy to switch to the unvoiced "-shn" pronuncia(-shn). The sound changes made to get from equate to that kind of equation reflect much the same shift as that to get from multiply to multiplication Commented Jun 21, 2023 at 2:01

4 Answers 4


I've read through all of the words beginning with a through c in WS2's very useful list of -tion words, and so far I've found that the vast majority of the words in the -tion family carry a sh sound at the beginning of the final syllable.

The main exceptions to that pattern are some words ending in -stion (bastion, combustion, congestion, counterquestion, countersuggestion, etc.) or in -ntion (attention, contention, convention, circumvention, etc.), which instead carry (in typical U.S. English) a ch sound at the beginning of the final syllable.

There is also a red herring in the form of cation, which is of course not a -tion ending at all, but a cat[a]- prefix attached to the root word ion.

Most significantly to the point of the OP's original question, none of the a through c words in WS2's list carries the sound zh at the beginning of the final syllable.

[One hour later...] I finished reading through all of the -tion entries at MoreWords.com, and the only one that—in my generic U.S. English pronunciation—has a zh sound at the beginning of its final syllable is equation. I should have taken Peter Shor's word (in a comment above) for it.

I did come across the variant spelling kation to go with cation, and I encountered one interesting exception to the -ntion exception that I noted earlier: To my ear, at least, dissention carries a sh sound (and not a ch sound) at the beginning of its final syllable; but dissention is a bit weird anyway because it is a variant of the more common spelling dissension.

Anyway, I am fairly confident that the answer to the question "How many -tion words are there whose last syllable sounds like the last syllable in vision?" is one.

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    Here's to brute effort!
    – ScotM
    Commented Feb 21, 2015 at 0:15
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    And honorary membership in the Brute Squad...
    – Sven Yargs
    Commented Feb 21, 2015 at 0:23
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    @Mari-LouA: Thanks for updating the broken link in my answer—much appreciated!
    – Sven Yargs
    Commented Aug 6, 2023 at 6:43

This seems to have been a change in the last hundred years or so. Walker's Pronouncing Dictionary from 1828, has "shun" and not "zhun", as does Webster's 1892 High School Dictionary (available via Google books).

It's possible both pronunciations were around in the 19th century, but clearly the /-ʃən/ pronunciation was considered "correct".

Since this appears to be a unique sound change that happened quite recently, it may be impossible to find a good explanation for why it happened.

For more evidence that this was a recent sound change, in his 1850 poem Misunderstandings, Lewis Carroll rhymes equation with observation and nation. The middle verse is as follows:

Now to commence my argument,
I shall premise an observation,
On which the greatest kings have leant
When striving to subdue a nation,
And e’en the wretch who pays no rent
By it can solve a hard equation.

(Note the unusual stress on the second syllable of the verb premise, which agrees with Walker's 1828 dictionary pronunciation for the verb: /priːˈmaɪz/.)


Edit: A while after making this post, I came across the entry for the word transition in Walker's Critical Pronouncing Dictionary (1823), which gives the pronunciation as "transizhun". The OED also lists this variant. Walker also lists a pronunciation with /ʒən/ for abscission. However, the explanation he gives for these irregular pronunciations does not apply to equation: he thinks that they are motivated by a desire to avoid having two voiceless sibilants in close succession.

The pronunciation of "abscission" with /ʒən/ seems to still be current, but the pronunciation of "transition" with /ʒən/ doesn't seem at all common today.

As other people have mentioned, there don't seem to be any other words spelled with -tion but pronounced with /ʒən/ except for equation.

The reason for the voicing in equation is not totally clear to me. Somewhat similar and possibly related phenomena are the voicing of /tʃ/ to /dʒ/ in various words ending in -ich/-itch (e.g. sandwich, ostrich; this seems to be pretty old and possibly influenced by analogy with the suffix -age) the voicing of /ʃ/ to /ʒ/ in words ending in -rsion (which seems to be fully accepted as standard now in the United States, although perhaps not so much in Britain), the voicing of /ʃ/ to /ʒ/ in fission (possibly by analogy with fusion; I'm not sure if this is fully accepted as standard anywhere yet) and the voicing of /tʃ/ to /dʒ/ in congratulation(s) (it's not universal, but it can be heard).


It may be that the ʒ sound in equation is phonetic over-exactitude. It may be that -tion after a long vowel-sound like /ei/ becomes automatically slightly vibrating. A fact, I suppose, only phoneticians were able to find out.

Daniel Jones, Pronouncing dictionary has ʒ and ʃ.

On the other hand, this is no general rule. Jones gives ʃ for nation. So I must say, I really don't understand the exceptional pronunciation of "equation". Probably only a professor of phonetics may be able to explain this.

But in my view, the problem of "equation" is of minor importance, one is understood no matter how you pronounce.

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    No, for me equation rhymes with persuasion, while relation and nation do not. And relazhun (real Asian?) sounds completely wrong. Commented Feb 23, 2015 at 18:21
  • @Peter Shor - The interesting question is why has equation this particular pronunciation.
    – rogermue
    Commented Feb 23, 2015 at 18:49

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