I was wondering about this for a while now. Could anyone explain this phenomenon or is it just "English quirks"?


  • invoke/invocation
  • provoke/provocation
  • revoke/revocation

4 Answers 4


The letters we think of as vowels 'a, e, i, o, u' are commonly associated with (at least) two different actual vowel sounds. These are so deeply embedded into the minds of English speakers that most speakers won't stop to think that in contemporary English there is no phonetic relationship between these vowels at all.

In British English RP we can observe the following relationships between these letters and some of the sounds they commonly represent:

  • A - /æ/, /eɪ/
  • E - /e/, /i:/
  • I - /ɪ/, /aɪ/
  • O - /ɒ/, /əʊ/
  • U - /ʌ/, /u:/

Notice that the sounds on the left are relatively short, and the ones on the right are longer. These symbols from British RP use a colon to represent length, or they use two symbols. You might also notice that the right hand sounds are actually the names of the letters involved. So the letter 'A' is actually pronounced /eɪ/. We can hear these different vowels being represented by these letters in the following pairs of words:

  • fat, fate
  • gen, gene
  • pin, pine
  • rot, rote
  • mut, mute

You will notice that one way that we represent the longer vowel sounds associated with these letters in the orthography is to put an 'e' after a single consonant at the end of a word.

This is what we see in the word invoke. The purpose of the E following the K in this word is to show that the O represents /əʊ/ and not /ɒ/.

Now in the word invoke we see this convention interacting with a different one. The letter C in English more often than not represents a /k/ when followed by the written vowels A, O and U as in the words cat, cot and cut. However, when followed by an E, I or Y it often represents an /s/ sound as in the words cent, cistern or cynic. Of course, we don't see this happening with the letter K, which always represents the hard sound /k/. We can observe this contrast, therefore, in pairs of words such as mace and make or lice and like.

In the word invoke we require the E to show that the O is representing a long /əʊ/ and not the short /ɒ/. If we spelled the word as either invoc or invok then a reader unfamiliar with the word would assume it rhymed with the word wok. Now if we just put an E after invoc so it was spelled invoce then an uninitiated reader would assume that the word rhymed with dose, because of the convention for using C to represent an /s/ sound when followed by E. In order to maintain the hard /k/ required, we need to use the letter K here.

Notice that in the word invocation, the C is followed by an A and so can therefore be used to represent the /k/ sound. The pattern that we see above is, of course, also seen in the other pairs of words listed in the question.

  • 6
    +1. On the principle that pairs of actual common words might be preferable, I suggest cute/cut for u--but what for e? The closest I can come is pet/Pete. Why are word pairs showing this pattern so few for the vowel e, I wonder? Commented Nov 4, 2015 at 14:50
  • 4
    @BrianDonovan I was wondering that too. I think it might be because we have a preference for using double E in comparable situations, perhaps? Commented Nov 4, 2015 at 14:51
  • 6
    @Tevis Because we can represent the /k/ there with a C because it is followed by A, not E. This also respects the derivation of the word (from the Latin vocare) :) Commented Nov 4, 2015 at 15:27
  • 10
    I suspect this is similar to the reason that American English uses "center" rather than "centre", but doesn't replace "massacre" with "massacer" Commented Nov 4, 2015 at 15:53
  • 2
    Nice presentation of the RP vowel system. Ain't English spelling fun? Commented Nov 4, 2015 at 16:28

Actually, invocation comes from the Latin invocatio(n), from the verb invocare, via Old French; invoke comes from French invoquer, from the Latin invocare.
in the first case the word derives from a word containing ca, which is maintained in the English word; in the latter case, the word derives from a French work containing que, which has been changed in ke.

There are some words that derives from a word in another language that contains que. In some cases, the que part is changed in ke; in other cases, the que part is kept in English too. For example, conquest derives from the Old French conquest(e), which comes from the Latin conquirere; conquer derives from Old French conquerre, which comes from the Latin conquirere.

  • 2
    +1 I was going to post that one "que -> ke", I think it's most likely that the words developed like that.
    – Alenanno
    Commented Aug 12, 2011 at 13:24
  • 3
    Yes. The OED gives the forms "invoque", "invoak" and "invoke" as historical spellings for "invoke" in English - it has apparently never been "invoce". Really it's parallel with pairs like "canticle/chant", where one came direct from Latin and the other through French; but in most cases this affected the pronuncation, but here only the spelling.
    – Colin Fine
    Commented Aug 12, 2011 at 13:27
  • There's invoice, literally a bill that invokes payment, where voke relates to vox, "voice". Wiktionary doesn't find it reasonable to source the claim that invoice came from Middle French envois [then why not envoys?!], plural of envoi [why from the plural?] via envoyer, "to send", that were from Late Latin inviare, via via, "way" (abl. "by way of"), that has two proposed etymologies. I guess, via, invoice and maybe vox might be convoluted wanderworts, given the themes (travel, post), infused with a pinch of folk believe.
    – vectory
    Commented Apr 29, 2019 at 18:00
  • @kiamlamuno The two examples you give of que being kept in English have Latin origins with qui compared to ca in invocare for invoquer. Do you think that's systematic? L qui -> OF que -> E que vs. L ca -> OF que -> E ke
    – Yogh
    Commented Oct 17, 2019 at 19:16

Actually, taking a look at their etymologies, you'd be expecting "invoke" to be spelt "invoce"!

Their roots are:

invoke: late 15c., from M.Fr. envoquer (12c.), from L. invocare "call upon, implore," from in- "upon" (see in- (2)) + vocare "to call,"

Invocation: late 14c., "petition (to God or a god) for aid or comfort; invocation, prayer;" also "a summoning of evil spirits," from O.Fr. invocation (12c.), from L. invocationem, noun of action from pp. stem of invocare

So, they've got the exact same root, but why is "invoke" spelt "invoke", or "invocation" spelt "invocation"?

My conjecture is that "invoce" was deemed easily confused in pronunciation (Invose?) as it is followed by an "e", and so, to reaffirm its "k" sound, they wrote it as "invoke" instead of "invoce". "Invocation" is followed by an "a", so change of spelling was not necessary.

And by the way, yes, that's the correct word.

  • 3
    Why should it be "invoce"? You don't give explanations for this. I find it most likely to be something like "invo[que]r" -> "invo[ke]".
    – Alenanno
    Commented Aug 12, 2011 at 13:28
  • 3
    It's pretty directly explained in the first line of the quoted passage; "invoke" is derived from "invocare". In latin, "c" is a hard k sound, so when it mutated to English, the letter eventually changed because "c" is ambiguous in that syllable (voce). Likewise, the "c" is non-ambiguous (or at least less ambigious) in the syllable "-cation", so the letter never morphed.
    – matthias
    Commented Aug 12, 2011 at 16:03

For "invocation," your cognate should be "vocal." The spelling of "invoke" was likely a convention adopted in spite of the etymology.

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