Identifying and non-identifying clauses: the tall man who …; Mr Rogers, who …

Two kinds of relative clause

Some relative clauses identify or classify nouns: they tell us which person or thing, or which kind of person or thing, is meant. (In grammars, these are called ‘identifying’, ‘defining’ or ‘restrictive’ relative clauses.)

• What’s the name of the tall man who just came in?
• People who take physical exercise live longer.
• Who owns the car which is parked outside?
• Have you got something that will get paint out of a carpet?

Other relative clauses do not identify or classify; they simply tell us more about a person or thing that is already identified. (In grammars, these are called ‘non-identifying’, ‘non-defining’ or ‘non-restrictive’ relative clauses.)

• This is Ms Rogers, who’s joining the company next week.
• In 1908 Ford developed his Model T car, which sold for $500.

There are several grammatical differences between the two kinds of relative clause. There are also stylistic differences: non-identifying clauses are generally more formal, and are less frequent in informal speech.

Pronunciation and punctuation

Identifying relative clauses usually follow immediately after the nouns that they modify, without a break. They are not separated by pauses or intonation movements in speech, or by commas in writing. (This is because the noun would be incomplete without the relative clause, and the sentence would make no sense or have a different meaning.) Non-identifying clauses are normally separated by pauses and/or intonation breaks and commas. Compare:

• The woman who does my hair is from Poland.
  Dorota, who does my hair, is from Poland.
• She married someone that she met on a bus.
  She married a very nice young architect from Belfast, whom she met on a bus.

If an identifying clause is left out, the sentence may not give enough information to make sense.

• The woman is from Poland. (Which woman?)
• She married someone. (!)

When a non-identifying clause does not come at the end of a sentence, two commas are necessary.

• Dorota, who does my hair is from … (not Dorota, who does my hair is from …)

Use of that

That is common as a relative pronoun in identifying clauses. In non-identifying clauses, that is unusual. Compare:

• Have you got a book which/that is really easy to read?
  I lent him ‘The Old Man and the Sea’, which is really easy to read. (not … ‘The Old Man and the Sea’, that is really easy to read.)
• Where’s the girl who/that sells the tickets?
  This is Naomi, who sells the tickets. (not This is Naomi, that sells the tickets.)

Leaving out object pronouns

In identifying relative clauses, we often leave out pronouns if they are objects, especially in an informal style. In non-identifying clauses this is not possible. Compare:

• I feel sorry for the man she married.
  She met my brother, whom she later married. (not She met my brother, she later married.)
• Did you like the wine we drank last night?
  I poured him a glass of wine, which he drank at once. (not I poured him a glass of wine, he drank at once.)

note

For sentences like It was Jack who told the police (‘cleft sentences’), (see here).