Grammatical Mission Impossible: Defining a Sentence

Begin every sentence with a capital letter.
What is a sentence?
Something that begins with a capital letter.
(Frank Smith, Writing and the Writer, 2nd ed. Lawrence Erlbaum, 1994)

Sure, we all recognize a sentence when we see or hear one. And most of us probably recall the textbook definition of a sentence as "a group of words having a subject and a predicate and expressing a complete idea."

But wait.

It's not that simple. Not at all.

For one thing, many word groups that contain a subject and predicate aren't sentences. For another, it's quite a stretch to say that all sentences express a single "complete idea." (Nobody, says James Hurford, "has a single reliable idea about how to identify 'a single idea.'") And if you've ever tried to explain how an absent subject or verb may be "understood," you know how easy it is to wind up talking in circles.

In her book Developing Language and Literacy (Sage, 2001), Ann C. Browne illustrates the difficulty of defining a sentence:

When adults try to explain what is meant by a sentence and therefore where to place a full stop, they may use phrases such as:

• a complete thought
• a group of words that make sense
• where you stop
• where your voice falls
• where you take a breath

Complete thoughts and groups of words could refer just as well to phrases as to sentences, and stopping places, particularly during the composing process, may occur virtually anywhere. In the Kingman Report (DES, 1988a) a sentence is described as "what it is that is enclosed between a capital letter and a full stop," but this still leaves the problem of what should be enclosed.

So never mind the "adults." What do the experts have to say?

• A sentence has been defined in various ways; but the best definition for our purpose is this: It is a form of words in which something is said about something.
  (Walter Marlow Ramsay, A Treatise on the Grammatical Analysis of Sentences, 1875)


• A sentence is a (relatively) complete and independent unit of communication (or--in the case of a soliloquy--what might be a communication were there someone to listen to it)--the completeness and independence being shown by its standing alone or its capability of standing alone, i.e. of being uttered by itself.
  (Otto Jespersen, Essentials of English Grammar, 1933)


• It is evident that the sentences in any utterance are marked off by the mere fact that each sentence is an independent linguistic form, not included by virtue of any grammatical construction in any larger linguistic form.
  (Leonard Bloomfield, Language, 1933)


• [W]e may distinguish sentence (a grammatically autonomous unit) from utterance (a unit which is autonomous in terms of its pragmatic or communicative function).
  (Randolph Quirk et al., A Comprehensive Grammar of the English Language. Longman, 1985)


• [A]n orthographic sentence is a unit of writing that begins with a capital letter and ends with a full stop, question mark, or exclamation mark. The term 'orthographic sentence' embodies no commitment as to whether or not the unit concerned is syntactically a sentence, a question which may have no determinate answer.
  (Rodney Huddleston and Geoffrey K. Pullum, The Cambridge Grammar of the English Language. Cambridge University Press, 2002)

As Katharine Perera has observed, "[T]here is no denying that linguists find it exceptionally difficult to produce a watertight definition of even such a common term" (Understanding Language, 1987).

And in the end, maybe that's not terribly important, as long as we can recognize the clues that signal the presence of a sentence.

So let's start again: "A sentence is something that begins with a capital letter . . .." Which works until we run across a sentence that opens with bicaps: "iPods have won several awards."

I give up.

Your mission, if you choose to accept it, is to compose a foolproof definition of sentence.

More About Sentences:

• Basic Sentence Parts and Structures
• Kernel Sentences
• What Is Sentence Combining and How Does It Work?

Blackboard: four functional types of sentences: (1) declarative, (2) interrogative, (3) imperative, and (4) exclamatory