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I often hear people saying that "I am" is the shortest sentence in the English language. I know that there are also discussions about sentences using the imperative mood such as "Go." that would be shorter, but my question is this:

Why would we (the people saying "I am" is a full sentence) not accept "I'm" as a complete sentence? Is there some unwritten rule about contractions that says "I'm" wouldn't be correct?

marked as duplicate by RegDwigнt Sep 29 '13 at 23:03

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    Related (and some good reading): english.stackexchange.com/… – J.R. Sep 13 '13 at 0:28
  • Thanks, @J.R. Interesting to see a somewhat wishy-washy-sounding rules from the CGEL. – SimonT Sep 13 '13 at 0:40
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    Did you mean to link to this question @J.R.? – terdon Sep 13 '13 at 0:50
  • Maybe people just don't think about answering the question with I'm. There reaction is to say I am. – user51891 Sep 13 '13 at 1:19
  • @terdon - no, I meant to link to the whole list. This one and this one discuss this matter as well. So does this one. There may be others; I didn't check them all. – J.R. Sep 13 '13 at 8:56
up vote 6 down vote accepted

In English, any clause has one mandatory stress slot: there must be at least one element that has stress (optionally more than one). That slot lies in the predicate of the clause, which must always be stressed. The subject (which stands outside the predicate) can receive stress, but does not necessarily have to, and even when it does receive stress, the predicate retains its stress.

Within the predicate, a verb that has one or more complements of a certain type (a generic object [i.e., one without an article], an adverbial phrase, a predicative expression, etc.) is unstressed (or at most secondarily stressed) unless it is emphasised for effect. In such a case, the predicate’s only stressed element(s) is/are the complement(s) that is/are considered most important.

Conversely, if the verb either does not have any compliments or has a non-generic object (i.e., an object with an article, a proper noun, etc.), it is stressed. Any following complements can also be stressed, but they do not have to be.

So for example (using the IPA character “ˈ” before a word to indicate stress, and the entirely ad hoc notation “ˣ” to specifically denote lack of stress):

He ˈran.
He ˣran ˈhome.
He ˈran a ˈmile.
He ˣran ˈfast.

As mentioned above, complements also include predicative expressions like subject and object complements—like what you have in ‘to be’ phrases. These follow the same rules (note that the distinction between generic and non-generic elements goes only for objects, not for predicative expressions):

He ˣis a ˈman.
He ˣis ˈgood.

Now very importantly: a stressed syllable cannot be syncopated. Only unstressed (or sometimes secondarily stressed) syllables can be syncopated away, leaving contractions in their wake. Of course, when you contract something, you are removing a syllable, and if that syllable is stressed, where would the stress go when you remove it? There has to be a stress somewhere.

As such, the following is possible:

He ˣis my ˈfather --> He’s my ˈfather.
I ˣcan ˈtell you ˈwhy --> I c’n ˈtell y’ ˈwhy.

– because the elements that are syncopated (is in the first, can and you in the second) are both unstressed. The following, however, is impossible, because here we’ve emphasised (= stressed) the verbs. Emphasising an element reduces other elements nearby to lose their stress entirely—it’s basically overriding the ‘natural’ assignment of stress—and the emphasised verbs end up being the only elements that carry any stress. If you syncopate those away, the stress would disappear entirely from the clause, which is not possible:

But he ˈis my ˣfather --> †But ˣhe’s my ˣfather.
I ˈcan tell you ˌwhy --> †I ˣc’n tell y’ ˣwhy.

Now recall that the predicate must be stressed. In a case like “I am” (with nothing more following the verb), where the verb has no complements at all, there is only one element that can be used to fill this stress slot: the verb itself, which is thus automatically stressed. And since the verb is stressed, it cannot be syncopated or contracted: that would remove the mandatory stress slot altogether, which is not an option.

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    That's an interesting answer. Can you add some sources? – TsSkTo Sep 13 '13 at 13:29
  • This is an interesting description of some elements of English stress patterns... though I'm not sure it actually accounts for why contractions are not used with ellipsis. – Neil Coffey Sep 13 '13 at 13:52
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    @TsSkTo normally when one or more sources are provided the answer's validity is improved. But in the case of Janus Bahs Jacquet, the sheer quality and the underlying sense of authority behind his detailed answer is such that I, for one, am left without any doubt that he knows what he is talking about. Now, whether his research and opinion is one I agree with, that is a separate issue. – Mari-Lou A Sep 13 '13 at 14:00
  • It's an interesting answer, but I think it does have the slight issue that contractions are used in stressed syllables for focus and topicalisation (e.g. "I'M doing it, not you"). So you would still expect e.g. "Who's doing it? I'M", but this turns out to be ungrammatical. – Neil Coffey Sep 13 '13 at 14:41
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    Note that "I'm doing it" means "I am doing it" and not "I am doing it," which is consistent with Janus's explanation. – Bradd Szonye Sep 18 '13 at 1:24

It’s because personal pronouns followed by contractions of the forms of be and have don’t occur in sentences on their own. For example, the answer to the question ‘Who’s going to the movie tonight?’ has to be I am and not I’m. Again, the answer to the question ‘Who’s seen this movie?’ has to be We have and not We’ve.

  • Well, yes but why? – terdon Sep 13 '13 at 12:30
  • I would guess it's simply because they don't give enough information. – Barrie England Sep 13 '13 at 12:35
  • Surely if I'm here gives enough information, so should Here I'm. Why would one have less information than the other? – terdon Sep 13 '13 at 13:34
  • Why? Just 'coz that's the way it is...! – Neil Coffey Sep 13 '13 at 13:53
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    @NeilCoffey that's a patronising reply if ever I heard one. Terdon's question is perfectly appropriate. To claim that "I am" gives more information that "I'm" is begging the question, why. – Mari-Lou A Sep 13 '13 at 14:04

It is hard to explain. The English language has a lot of little things that can be put in different places but that will mean the same thing. "I am" versus "I'm" is a perfect example of this. It is more of how you were raised on hearing "I am" you use "I am" not "I'm". You wouldn't say "The time is what?" you would say "What time is it?"

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    -1. This doesn’t really answer the question at all. Moreover, it is very hard to understand and doesn’t make any proper sense, really. – Janus Bahs Jacquet Sep 13 '13 at 13:00

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