<p>Just four examples of context sensitive (i.e. non context free) sentences in English; <em>the first is embedded here and - like the second and the third - implies counting, the last one is a polysemy</em>.</p>

<p>The colors of the three balls are red, blue and green respectively.</p>

<p>London, Paris and Madrid are the capitals of England, France and Spain</p>

<p>The dog is eating an hot dog</p>

CC BY-SA 3.0
2013-04-02T09:49:33.967Z
2013-04-02T09:49:33.967Z
Marzio De Biasi
<p>When I say 'equally familiar natural language', I hope to ignore languages such as Arabic and Hebrew, of which I know absolutely nothing save an alphabet in the latter case.</p>

<p>I am doing research in named-entity recognition and social network analysis in English literature using the <a href="http://www.nltk.org" rel="nofollow">Natural Language Toolkit for Python</a>.  The goal of my research is to determine the strength of relationships between characters (taking into account difficulties such as aliases, etc.)</p>

<p>I've seen several resources declaring that 'grammatically-correct' English is context-sensitive, almost always relying on the peculiarities of our verbs.  However, if we removed the need to be 'grammatically-correct' and instead focused on only the <em>gist</em> of the English sentence,</p>

<ul>
<li>could we describe English* as context-free?</li>
<li>could it be proven either way?</li>
</ul>

<p>To make my definitions objective, I mean <em>gist</em> in a way that preserves the relationships between entities disregarding temporal context, e.g. <em>The dog bit Dracula</em> is 'equivalent' to <em>dog bite Dracula</em> (the words in the sentence are reduced to their stems, you could say).</p>

<hr>

<p>Edit per the comments.<br>
Yes this is motivated by NLP, but I suppose I'd more like to know what a language defined by a production ruleset such as $$S\to NP\ VP\\NP\to Det\ Adj\ Noun\\VP\to Verb\ Object\\etc.$$ would look like.  Since it would defined by a CFG it would obviously be context-free, so practically I could reduce the text down to stems and parse it this way.</p>

<p>While this may or may not be a research-level question, it's a question that has definitely come up in my research.</p>

CC BY-SA 3.0
2013-04-02T02:30:14.070Z
Probably not. Secondly, this is a question about NLP not CS algorithms/theory... Not the right place for this question.
Sariel Har-Peled
CC BY-SA 3.0
2013-04-02T07:15:22.203Z
If we remove the need to be gramatically correct, in what sense is it English?  Voting to close as "not a real question".
Jeffε
CC BY-SA 3.0
2013-04-02T09:08:07.967Z
Perhaps I was unclear - Yeah this is NLP, but I'm generally interested if, removing the finer points of grammar, natural languages would fall into some class of languages that is already well-described.  I'll edit my question.
Sean Allred
CC BY-SA 3.0
2013-04-02T11:21:32.403Z
(a) this question is not well formed, (b) this is a linguistics question, and (c) it is not research level. Have you [consulted wikipedia](http://en.wikipedia.org/wiki/Context-free_grammar#Linguistic_applications)?
Artem Kaznatcheev
CC BY-SA 3.0
2013-04-02T13:03:56.790Z
A) I would agree B) I wouldn't very well be able to ask it on English.SE C) I know *exactly* what context-free language is, but haven't the foggiest on how one could apply the pumping lemma (or any other method) to this language, which is itself not well-defined.
Sean Allred
<fl.formal-languages><context-free-languages>
Is the gist of English (or any equally familiar natural language) context-free?
Sean Allred
# Is the gist of English (or any equally familiar natural language) context-free?

(Asked by: username_0 on 2013-04-01)

When I say 'equally familiar natural language', I hope to ignore languages such as Arabic and Hebrew, of which I know absolutely nothing save an alphabet in the latter case.

I am doing research in named-entity recognition and social network analysis in English literature using the [Natural Language Toolkit for Python](http://www.nltk.org). The goal of my research is to determine the strength of relationships between characters (taking into account difficulties such as aliases, etc.)

I've seen several resources declaring that 'grammatically-correct' English is context-sensitive, almost always relying on the peculiarities of our verbs. However, if we removed the need to be 'grammatically-correct' and instead focused on only the *gist* of the English sentence,

* could we describe English\* as context-free?
* could it be proven either way?

To make my definitions objective, I mean *gist* in a way that preserves the relationships between entities disregarding temporal context, e.g. *The dog bit Dracula* is 'equivalent' to *dog bite Dracula* (the words in the sentence are reduced to their stems, you could say).

---

Edit per the comments.  
Yes this is motivated by NLP, but I suppose I'd more like to know what a language defined by a production ruleset such as $$S\to NP\ VP\\NP\to Det\ Adj\ Noun\\VP\to Verb\ Object\\etc.$$ would look like. Since it would defined by a CFG it would obviously be context-free, so practically I could reduce the text down to stems and parse it this way.

While this may or may not be a research-level question, it's a question that has definitely come up in my research.

**Tags:** fl.formal-languages, context-free-languages
> **Comments:**
> **username_1**: Probably not. Secondly, this is a question about NLP not CS algorithms/theory... Not the right place for this question.  
> **username_2**: If we remove the need to be gramatically correct, in what sense is it English?  Voting to close as "not a real question".  
> **username_0**: Perhaps I was unclear - Yeah this is NLP, but I'm generally interested if, removing the finer points of grammar, natural languages would fall into some class of languages that is already well-described.  I'll edit my question.  
> **username_3**: (a) this question is not well formed, (b) this is a linguistics question, and (c) it is not research level. Have you [consulted wikipedia](http://en.wikipedia.org/wiki/Context-free_grammar#Linguistic_applications)?  
> **username_0**: A) I would agree B) I wouldn't very well be able to ask it on English.SE C) I know *exactly* what context-free language is, but haven't the foggiest on how one could apply the pumping lemma (or any other method) to this language, which is itself not well-defined.  

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## 1 answers

### Answer by username_4 on 2013-04-02. Score: 2

Just four examples of context sensitive (i.e. non context free) sentences in English; *the first is embedded here and - like the second and the third - implies counting, the last one is a polysemy*.

The colors of the three balls are red, blue and green respectively.

London, Paris and Madrid are the capitals of England, France and Spain

The dog is eating an hot dog


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