The Wikipedia article on Generative Grammar states:

Generative grammar is a linguistic theory that regards grammar as a system of rules that generates exactly those combinations of words that form grammatical sentences in a given language.

GG tree diagrams always have a symbol S at the apex, representing "sentence". There is no higher level.

On a question I asked on the English Language & Usage site about "What to do?" I've been told that's a valid question but that it's not a sentence:

Just as not all sentences are questions, not all questions are sentences. That doesn’t make them ungrammatical. They simply aren’t sentences, since all sentences have a subject and a finite verb.

Does this mean that there are two conflicting meanings of "sentence"? If "What to do?" is not a sentence, is that a peculiarity of GG? What should it be called instead? Is there a level higher than "sentence" which covers both "sentence" and things such as "What to do?"?

  • Who says that John Lawler's comment is the definitive "usual" meaning of "sentence"? I've got lots of respect for John, but he isn't always right, and he doesn't speak for everyone.
    – curiousdannii
    Apr 12, 2018 at 12:45
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    @curiousdannii: That's what I'm asking. I'm just looking for an answer. I apologize for my lack of skill in crafting the question. What do you recommend I use instead of "usual"? I don't know anything about John Lawler other than that tchrist used him as an authority in his argument. Apr 12, 2018 at 12:59
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    Hmm, I guess you could phrase it more neutrally by asking which of the two is the more conventional definition.
    – curiousdannii
    Apr 12, 2018 at 13:42
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    @curiousdannii: I just tweaked the title a little. It's after midnight here so I'll have another look in the morning. You may also tweak it if you like. Apr 12, 2018 at 14:26

2 Answers 2


I think we can confidently conclude that there are two or even more conflicting definitions of "sentence". Analogously, there are multiple definitions of "markedness". However, your first quote:

Generative grammar is a linguistic theory that regards grammar as a system of rules that generates exactly those combinations of words that form grammatical sentences in a given language.

is not a definition of "sentence", it is a claim about GG and what a grammar does does. I will leave aside the question of whether it is accurate as a characterization. If this claim is true, we might infer some definition of "sentence", but it isn't a definition.

I presume that your real question is about some claim, and not the definition of "sentence", but I'm not entirely sure what the claim in question is. The primary question, I think, is a version of the old competence / performance problem: is "what to do?" grammatical, or merely acceptable? If this string is grammatical, then (by definition) it is generated by the grammar, and the claim that (grammars only generate sentences and all sentences have subjects and verbs) is false. That is, at least one of those claims is false, possibly both. If the string is ungrammatical but acceptable, then we learn nothing about what a grammar does.

The claim that every sentence has a subject and a finite verb has a consequence, that imperatives are also not sentences. Forget that, I say. It also means that many utterances in languages without verbal copulas are not sentences. Perhaps (indeed, almost certainly), the claim was intended to be about English, not the concept "sentence", but GG is not a theory of English, it is a theory of language (despite initial appearances). We could say that the claim is not a claim about surface word order, it's a claim about logical form, so that there are always elided finite verbs or deleted subjects, but that "What to do?" would come from "What should we do?". Similarly, "Banana" could be the sort form of a number of sentences, such as "I'll have a banana" or "The English word for 'banana' is 'banana'".

There is no good way to assess the social construct of conventionality, because there's no system of opinion-polling / voting. One may reach certain surmises by looking at the literature to see what certain people say, and perhaps that it the only operationally-sensible way to talk about conventionality of concepts. Each publication is weighted according to impact factor of something like that, and if high-impact papers tend to converge on a particular conclusion, that is what counts as "conventional". I presume the problems with this approach are obvious.

  • 'What to do' is a noun phrase, and can be used as a sentence fragment. It can function as a sentence only in a context where the missing items can be reconstructed. Imperatives are not fragments, as they are well-defined (subject=you ...) and do not rely on context.
    – amI
    Apr 12, 2018 at 21:04
  • The back-story is convoluted. 'What to do' is in a Chinese course and some native English speakers claimed nobody says that. I thought some people do so asked about it on ELL to be more informed. Respondents on ELL objected to me labelling it a sentence. I didn't find a good definition of "sentence" but know a bit about recursive parsing and knew "sentence" is the top level in that discipline. The paragraph from wiki's GG was something I found that matched. I'm trying to fill all my knowledge gaps as I investigate. Apr 13, 2018 at 2:06
  • IMO, massive confusion arises when one attempts to encode all knowledge about a topic in its definition. You know what "sentence" means: but you may not know what all of its properties are. If you learn a new fact about sentences, that does not mean that you didn't previously know what "sentence" refers to. Detection criteria really should not be in the definition of a concept: they are separate.
    – user6726
    Apr 13, 2018 at 15:04

How to find out what category an expression is in? How to decide? When to worry about it? Who to ask? When to accept a proposed answer?

Since expressions of the same category can be coordinated, where to seek evidence, how we should construct examples, and why not to doubt their significance seem relevant.

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