In Grammar 4-1 and 4-2, you focused on using defining relative clauses. In this lesson, you are going to look at non-defining relative clauses.
Non-defining relative clauses are relative clauses that contain additional or non-essential information about the noun that they modify.
Remember!
When you use a non-defining relative clause, you cannot omit the relative pronoun under any circumstances, even if it is the object of the clause.
- Niagara Falls, we visited last summer, is one of Canada’s most famous natural places. (incorrect)
- Niagara Falls, which we visited last summer, is one of Canada’s most famous natural places. (correct)
You cannot introduce a non-defining relative clause with the relative pronoun that. You need to use who(m) or which instead.
- Niagara Falls, that we visited last summer, is one of Canada’s most famous natural places. (incorrect)
- Niagara Falls, which we visited last summer, is one of Canada’s most famous natural places. (correct)
In writing, you always surround a non-defining relative clause with commas.
- Niagara Falls which we visited last summer is one of Canada’s most famous natural places. (incorrect)
- Niagara Falls, which we visited last summer, is one of Canada’s most famous natural places. (correct)
Adding Extra Information
The main reason that non-defining relative clauses are used is to add extra information that may be of interest. Look at these examples
- Vancouver, which is located on the west coast, has one of the mildest climates in Canada.
- David Suzuki, who began his career as a geneticist, is one of Canada’s most celebrated environmental activists.
- Denali, which is 6,190 m high, is the tallest mountain in North America.
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