Commas Setting Off Non-restrictive Modifiers
A non-restrictive clause is a clause which may offer more information, but doesn’t limit
the subject; this might be something of interest, such as how old something is or a job a
person has. A non-restrictive clause may use the word which and can be removed from
the sentence without loss of understanding.
Non-restrictive clauses are generally separated from the rest of the sentence by
commas (while restrictive clauses are not).
That box of apples, which I picked this morning, can be used to make the pie.
The non-restrictive clause which I picked this morning needs to have a comma on
either side of it because this information is not required to identify the box; that is
the word which identifies the box (we can assume the speaker is pointing to it).
Three years ago, the house on the corner, which was of historical interest, was torn
down.
As the house is already identified as the one on the corner, the fact that it was of
historical interest is not necessary.
Commas can also be used with appositives. An appositive is a noun or noun phrase
that renames a nearby noun. Appositives offer nonessential information. Nonrestrictive
appositives are set off with commas; restrictive appositives are not.
Alexander Pope, the Restoration poet, is famous for his monologues.
The appositive is “the Restoration poet.” Since this information is not required for
the sentence to make sense, the appositive is set off with commas.
Practice
Each sentence contains a non-restrictive clause. Add commas in the correct places.
1. Great Expectations by Charles Dickens did not interest me.
2. William Carlos Williams the poet was also a farmer.
3. John who has been drinking should not drive.
4. In spring when the water is high the lake surges over the rocks.
5. The waiters dressed in their white jacket, are already arranging the chairs on the
sidewalk.
6. When I do yoga, I wear my favorite shirt which is really old.
7. For camp the children need sturdy shoes which are expensive.
8. Ed’s house which is located on thirteen acres was completely furnished with bats in the
rafters and mice in the kitchen.
9. The helicopter with its million-candlepower spotlight illuminating the area circled above.
10. Darwin’s most important book On the Origin of Species was the result of many years of
research.
11. John who spent the last three days fishing is back on the job again.
12. The New York Jets the underdogs surprised everyone by winning the Super Bowl.
13. Simon Blake a well-known lawyer may run for governor.
14. Marcia Gomes who was not sitting down just got a detention.
15. My uncle who is eighty years old walks three miles every day.