A relative clause is a clause introduced by a relative pronoun like who or which.
Two common types of relative clauses exit: defining (or identifying) relative clause and non-defining (or non-identifying) relative clause.
An identifying relative clause identifies the noun it refers to – that is to say, it tells us which person or thing is being talked about.
Consider the example given below.
- People who take physical exercise live longer.
Here the relative clause is who take physical exercise. This relative clause is identifying, since it is required for identification: without it, we would have only People live longer, which does not identify the people under discussion.
Other examples are given below.
- The restaurant which we visited last night was pretty good.
- Paris is a city I have always wanted to visit.
- She married a man that she met on a bus.
Identifying relative clauses usually follow immediately after the nouns that they modify, without a break: they are not separated 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.
A non-defining relative clause is not required for identification. It serves only to provide additional information. Non-identifying clauses are normally separated by commas.
- Janet, who does my hair, has moved to another hairdresser’s.
Here the relative clause is who does my hair. This relative clause is non-identifying, since it is not required to identify Janet: it merely provides additional information.
Another example is given below.
- She married a smart architect from Beijing, whom she met on a bus.
An adverb which introduces a relative clause. The English relative adverbs are where, when, wherever and whenever.
- The day when I met John was the best day of my life.
- Alice takes her cell phone wherever she goes.