English grammar - Roger Berry 2012
A9.1 The sentence
A9 Types of sentence
Section A. Introduction
Traditionally, the sentence is the highest unit of analysis in grammar. Sentences are composed of clauses, clauses of phrases, phrases of words, and words of morphemes (the smallest unit). But at each level of analysis, a higher unit may consist of only one unit of the lower level. So a phrase may consist of one word, as we have seen in a number of places. Indeed, it is possible for a sentence to consist of just one morpheme: Listen! In some approaches it is also maintained that there is a level of analysis above the sentence; see B11 for more on this.
Defining the sentence is not easy. One traditional, notional, definition is that sentences express one complete idea, but this has also been suggested for clauses. But when we try to define sentences formally, there is another problem: the popular idea of what a sentence is differs from the grammatical one. Most people, when asked, would say that a sentence is something that starts with a capital letter and ends with a full stop, question mark or exclamation mark.
There are two things wrong with this popular definition. First, it does not really help us to understand what a sentence is - why people put a full stop in a certain place and not elsewhere (and why, with a few exceptions, people agree on where full stops should go). Second, and more importantly, it can only be applied to writing, not speech. It is a ’graphological’ definition. Speech is just as valid a medium as writing, but there are no capital letters or full stops in it.
We could attempt a parallel ’phonological’ definition, which would apply to speech. It might go something like this: a sentence is a string of words that follows certain intonation patterns (e.g. falling for declaratives and wh- word interrogatives, rising for yes/no interrogatives). But this would be difficult to apply and would have many exceptions.
What we need is a grammatical definition, which would apply regardless of the medium, and there is one:
’A sentence is a string of words that follows the rules for forming clauses and combinations of clauses.’
The rules for forming clauses - in which the verb pattern plays the central role - were addressed in A8 and B8. The main aim of this section is to discuss the rules for the combination of clauses. The combination of clauses is a universal feature of English, whether spoken or written, and we need to explain how it happens. However, some grammarians have pointed out that it is not easy to separate some types of speech into sentences; an extreme claim is that the sentence is a graphological concept, but this book maintains that the grammatical definition offered above is valid. Grammatical sentences differ from graphological sentences in a number of ways. For example, in grammatical terms, the semi-colon also forms a sentence boundary. We will consider the issue of whether speech has sentences in A12.