I looked up possibility on Thesaurus.com,

but what I want to know is where the 'i' in possibility comes from?

Why not have 'possibile' or 'possiblity'?

  • 1
    Because. Really, that's the entire answer. There is no secret cabal of English Gods who are actively designing and dictating the language, no one is reviewing it to make sure it's self-consistent or logical ... in short, there is no governance. There is no "why"; language, like a tree, simply grows, and tiny accidents of history can result in long, twisty branches leading nowhere. It is spelled as it is spelled. Accept it and move on.
    – Dan Bron
    Feb 12, 2015 at 13:34
  • 2
    Not that I have the answer, @DanBron, but I have a hard time accepting "because" as an answer, either. There is a reason or history for the peculiarity of how a word is spelled. OP's not asking "why", he's asking where it comes from. Feb 12, 2015 at 15:06
  • How is possibility an exception, or any different from several other such "anomalies"? Or, is the OP using the word as a class-example?
    – Kris
    Feb 12, 2015 at 15:06
  • @LittleEva No, they got their tongues twisted way too much, rather.
    – Kris
    Feb 12, 2015 at 15:09
  • 1
    @KristinaLopez You're exactly right. Your comment spurred me on to write an answer ... You can find it below! :-) Feb 12, 2015 at 17:19

2 Answers 2


The reason is this: the word possible has three syllables. In the transcription /pɒsɪbl̩/, we can see a little mark under the /l/ which indicates that that the /l/ constitutes a whole syllable on its own. There is an alternative, slightly child-like pronunciation for this word, /pɒsɪbəl/. This uses the schwa vowel before the /l/ to make the nucleus of the final syllable (we can think of the nucleus like the body of the syllable).

Syllabic /l/, like syllabic /n/ is only found in unstressed syllables like this. There is nearly always an alternative pronunciation available with a schwa vowel, /ə/ instead. Schwa, like syllabic /n/ and syllabic /l/, also only occurs in unstressed syllables.

Now, here's the point. The suffix -ity, which is used to change adjectives into nouns, involves a stress rule. It dictates that the stress in the word occurs on the previous syllable. In other words the stress must move to the last syllable of the root word. This kind of stress rule is very common with suffixes in English. For example, the suffix -tion dictates that the stress moves to the previous syllable in exactly the same way. We can see the stress move when we add the suffixes to the following examples (stress is indicated by bold font):

  • con'taminate.
  • contami'nation.
  • ab'normal.
  • abnor'mality.

This rule causes an issue with certain adjectives, however. The following words are usually said with a syllabic /l/ at the end:

  • accessible
  • reliable
  • deniable
  • responsible.

Now if we want to stick the suffix -ity onto the ends of these words to make nouns, our rule says that the final syllable of the original adjective must now be stressed. However, we can't do this because we cannot have a stressed syllable in English that is a syllabic consonant. If you try to say:

  • possibleity

You will immediately notice that this sounds very odd - because it breaks the phonological rules of English. One solution to this is to put a vowel in the final syllable of the root. We can't however use a schwa, because as we noted above, schwa cannot occur in stressed syllables in English either. The solution to this problem is to insert the KIT vowel /ɪ/ in the final syllable. This allows us to put the stress on the correct syllable:

  • accessi'bility
  • relia'bility
  • denia'bility
  • responsi'bility

This is the sound being represented by the letter 'I'. Now that we have a stressable syllable here, everything is now ok with the world - sorry, I meant word.

Hope this is helpful!

  • 1
    +1 That was great instruction, though because it's all new to me it raised some new questions relating to your terminology. I could grasp the reasoning though. Thank you.
    – user98990
    Feb 12, 2015 at 17:52
  • i just looked up 'possibility' on a phonetic dictionary:speech.cs.cmu.edu/cgi-bin/cmudict?in=possibility&stress=-s (i was looking for one that made noises)
    – JMP
    Feb 12, 2015 at 21:19
  • 2
    @LittleEva Feel free to ask any questions. I'm quite happy to answer anything you might be wondering about. (It might help me improve the post too!) Feb 13, 2015 at 0:44
  • This only gives half the answer, though: it explains why it's not possiblity, but not why it's not possibile. There's no synchronic reason the phonemic schwa (or phonemic syllabic l if you believe in those) couldn't be represented orthographically by -ile the way it is in nubile, mobile, and labile (when not pronounced to rhyme with bile). The real answer to that is, as Roger points out, that the unstressed vowel was lost in Old French, and English has taken the OF spelling directly without modifying it, for both adjective and noun. Feb 13, 2015 at 2:07
  • i just got 'noble' -> 'nobility', so 'le' -> 'ility', but 'mobile' would then go to 'mobiility'
    – JMP
    Feb 13, 2015 at 15:20

In some respect your question is justified as the Latin adjective is pos'sibilis/possibile, the French form is aready shortened pos'sible and English has the French form but the stress on the first syllable 'possible. The Latin noun possi'bilitas/ possibili'tat-is (genitive) gives possibili'té in French and possi'bility in English.

Link to etymonline possible and possibility



  • +1 A link to a reliable source of etymology would help, too.
    – Kris
    Feb 13, 2015 at 6:04

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