OUR FORTNIGHTLY extract from the noted old school English usage guide, Gwynne’s Grammar. This week, we look at the humble comma.

OF ALL punctuation, the importance of the correct use of the comma is especially worth noting and studying; since using it or leaving it out can give radically different meanings to sentences which in every other way are identical. Examples:

1. My brother, who lives in London, is a teacher of grammar.

2. My brother who lives in London is a teacher of grammar.

In the first sentence I have only one brother; in the second, more than one brother.

1. Politicians who tell lies are to be despised.

2. Politicians, who tell lies, are to be despised.

In the first sentence only some politicians are to be despised; in the second sentence, all of them.

1. This morning he had a grammar lesson, which was very unusual.

2. This morning he had a grammar lesson which was very unusual.

In the first sentence it was very unusual for him to have a grammar lesson in the morning. In the second sentence he had a very unusual kind of grammar lesson.

How do we decide when to use the commas and when to leave them out? In technical language, the commas must be (a) omitted when the relative clause in question is a restrictive relative clause and (b) put in when it is a non-restrictive relative clause. Exactly what these clauses are and do, and why the one is used without surrounding commas and why they are needed for the other, is explained in different ways in various good books on English, including Professor Strunk’s little masterpiece reproduced in Part II. Let me see if I can come up with yet another explanation.

A restrictive clause is so closely bound up with the noun or noun-phrase it is describing that its use there restricts the meaning of – gives a special meaning to – that noun or phrase. So  much is this so that, although one would not do so in practice, one could theoretically hyphenate together every single word from the beginning of the noun or noun phrase to the end of the restrictive clause. Thus: “My-brother-who-lives-in-London-is-a-teacher…” – which of course leaves no room for a comma after “brother”. Without the restrictive clause attached to its noun or noun=phrase, the sentence would either make no sense or a completely different sense from what the writer intended.

A non-restrictive clause is a clause which, in effect, makes a separate statement within the sentence about the noun or noun-phrase. It could be left out without the essential meaning of the sentence it is in changing. Indeed the commas surrounding it perform the same function as brackets would – “as in “My brother (who lives in London) is a teacher…” – and commas or brackets are necessary for the correct use of the sentence.

One last thing to remember about these two different kinds of clauses is that, where there is a choice between “that” and “which” to introduce a clause, “that” should always be used to indicate restrictive clauses and “which” to indicate non-restirve clauses.

ENDS

This piece was extracted from Gwynne’s Grammar (Ebury Press). Our next Gwynne’s Grammar Tip will be published on Wednesday 11 March.