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In my experience, "finite" is pronounced (IPA) ˈfaɪnaɪt while "infinite" is ˈɪnfɪnɪt.

In general, the prefix "in" negates an adjective, but does not change the pronunciation. Based on this, I would expect ˈɪnfaɪnaɪt.

Is there a reason for this "deviation from the norm"? Are there dialects/regions that actually say ˈɪnfaɪnaɪt (or ˈfɪnɪt, for that matter)?

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Nitpick: I have /ˈɪnfəˌnɪt/, which I think is usual. (I speak AmE and have a mathematical background.) – Charles May 5 '11 at 17:06
Double nitpick: depending on your dialect, /ɪ/ may or may not be used in unstressed syllables. This gives either /ˈɪnfɪˌnɪt/ or /ˈɪnfəˌnɪt/. – Peter Shor Feb 12 '12 at 19:30
up vote 6 down vote accepted

I believe we pronounce infinite the way we do because a dactyl is simply easier to say, in most cases. It trips (quite literally) off the tongue. It seems we're forced into the spondee of finite, even though that is harder to say, because nothing else makes sense. But once that extra syllable has come to the rescue we can get lazy again.


After giving the matter more thought, I think we pronounce finite as a spondee because both syllables have the "long i" sound (aɪ). I can't think of a single instance of aɪ coming on an unstressed syllable. I think that's mainly true of all the "long" vowels as well, but I will not be surprised if someone can come up with an exception or three.

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Assuming this is true, are there other examples of this transformation? – ShreevatsaR Jan 8 '11 at 12:23
@ShreevatsaR: What about the difference between carbonate (as a verb such as: I carbonate my beverages at home) pronounced car-bon-eight and bicarbonate, which I often hear pronounced on television as bi-carb-o-nt (with the stress on the "bi"). It's not as pronounced as the difference between finite and infinite, but I think it can be attributed to the same phenomenon that Robusto is describing. – Andy F Jan 8 '11 at 12:37
»I think we pronounce finite as a spondee because both syllables have the "long i" sound ().« - Isn't that somewhat begging the question? I'm prepared to take the "lazy" argument, though, apparently it's behind many things that affect the English language. – Tomalak Jan 9 '11 at 17:33
@Tomalak: "Lazy" is behind EVERY human language, right after "get the message across somehow". – Mr. Shiny and New 安宇 Jan 10 '11 at 16:07
@Mr.Shiny: This might be so, but IMHO English is a particularly good example. – Tomalak Jan 10 '11 at 16:11

It's the three syllable rule that messes it up. Logically FI-nite would be in-FI-nite with the prefix, but as it becomes three syllables, the third syllable from the end is stressed and it becomes IN-fi-nite. When you stress the first syllable, you have to change the pronunciation to un-stress the second syllable.

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Why the downvote? If you don't explain what you think is wrong, it can't improve the answer in any way. – Guffa Jan 8 '11 at 13:18
Edited to correct your spelling of syllable ("syllible") and pronunciation ("pronounciation"). That was probably the basis of the objection. – Robusto Jan 8 '11 at 13:30
I think the downvote was because this answer doesn't seem to adequately answer the question. Obviously, there is a stress shift. OP is asking why this came about (historical, phonotactic, etc.) and whether there are parallel examples. The question was not what the difference is. – Steven Xu Jan 8 '11 at 15:38
@Robusto: Thanks for the corrections. The awkward pronunciations of those words keep fooling me... I hope that your theory that this would be the basis of the downvote is not correct. – Guffa Jan 8 '11 at 16:44
I always have to go back and correct the spelling of "pronounciation". The correct "pronunciation" makes no sense to me at all. ;-) So that three syllable rule is an "official" thing? – Tomalak Jan 9 '11 at 17:39

I believe its a matter of stress. IN-fi-nite. FI-nite. It is very awkward to say a word with two stressed syllables followed by one unstressed.

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But the syllable only appears to you as "stressed" since you are used to interpreting it this way. How would you pronounce Fein (yes, as in "The Nanny")? Does the "FI" it appear to you as stressed there? – Tomalak Jan 8 '11 at 11:15
Also, this doesn't explain why the word isn't, say, in-FI-nite. – ShreevatsaR Jan 8 '11 at 11:46
And actually, looking for reliable rules in language is futile (and I'm not really sure how you pronounce that ;-)). There's a "Houston Street" in NYC. Guess how that's pronounced ;-) – Jürgen A. Erhard Jan 8 '11 at 22:47

I think Robusto is right that it is related to stress. The stress change causes the unstressed vowel after the prefix to become reduced.

You say that "in general, the prefix "in" negates an adjective, but does not change the pronunciation." I would agree with that, but note that normally the prefix "in-" is also unstressed, even when it is the third syllable from the end : look at the word infertile /ɪnˈfɜrtəl/, which is the negative counterpart to fertile /ˈfɜrtəl/.

So, I think we have to differentiate two versions of the prefix: the more common and productive version in1- does not take stress and does not change the pronunciation; but there is another, rarer prefix in2- that does take stress and may cause other changes in pronunciation. This distinction also applies to some other prefixes, by the way, such as re-, de- and pre (compare definite and deform). Obviously, both versions of the prefix have very similar meanings, and in some cases different speakers may use different versions. But I have not heard of anyone saying /ɪnˈfaɪnaɪt/, so I think this particular word only exists with the prefix in2-.

Here are some more words with in2-:

Some of these are valid words without the prefix, others are not.

Comparing words with and without the prefix, we can see the kind of sound changes it causes:

  • famous /ˈfeɪməs/, infamous /ˈɪnfəməs/
  • potent /ˈpoʊtənt/, impotent /ɪmpətənt/
  • pious /ˈpaɪəs/, impious /ˈɪmpiəs/

The prefix does not only receive stress, it converts the following syllable into a fully unstressed syllable. In English, vowels in unstressed syllables are reduced.

So that explains part of the difference. I'm still not sure exactly why there is a difference in the pronunciation of the final syllables of finite and infinite.

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This is very systematic and informative, thank you! – Tomalak Feb 20 at 23:45

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