Updated September 2023
Some writers find that the trickiest sentences to punctuate are those that include clauses beginning with words such as who, that, and which. Clauses of this type are called relative clauses, and the key to correct punctuation is to understand whether the clause in question is restrictive or nonrestrictive. Following are some guidelines to help.
What is a clause? First, remember that a clause is simply a group of words that contains at least one subject and at least one verb. There are two main types of clauses:
Independent Clause: Also called a sentence, this clause expresses a complete thought.
Example 1: The boy had been missing for three days.
Subordinate Clause: Like all clauses, this clause contains at least one subject and at least one verb; however, subordinate clauses do not express a complete thought. Instead, they are dependent upon the rest of the sentence for their meaning.
Example 2: The boy who had been missing for three days was found at his friend’s house in Texas.
In this sentence, the subordinate clause who had been missing for three days is dependent upon the independent clause (The boy was found at his friend’s house in Texas). In other words, the subordinate clause could not stand on its own as a complete sentence.
Relative clauses are a type of subordinate clause. They often begin with a relative pronoun such as who, that, or which, and they answer the following questions: Which one? What kind? How many?
In example two, because the subordinate clause begins with who, we can also call it a relative clause. It tells us which boy was found at his friend’s house in Texas.
There are two types of relative clauses: restrictive (also called essential) and nonrestrictive (also called nonessential).
A restrictive clause is a clause that is essential to the meaning of the sentence. In other words, if you removed the restrictive clause, the sentence’s meaning would not be the same.
A nonrestrictive clause is a clause that is not essential to the meaning of the sentence. If you removed the nonrestrictive clause, the meaning of the sentence would stay the same. Nonrestrictive clauses simply impart extra information that is not necessary to the main idea of the sentence.
There are two important points to remember about restrictive and nonrestrictive clauses:
1. Restrictive clauses are not set off by commas. Nonrestrictive clauses are set off by commas.
2. Generally, the pronoun that should be used with restrictive clauses and which should be used with nonrestrictive clauses. The pronoun who can be used with both restrictive and nonrestrictive clauses.
Let’s look at some examples:
Example 3: The book that is lying on the coffee table belongs to Cherie.
Example 4: The book, which is lying on the coffee table, belongs to Cherie.
At first glance, these sentences may appear to be very similar. However, their meanings are very different. In example three, the relative clause that is lying on the coffee table is restrictive; it is essential to the meaning of the sentence. It tells us which book out of many belongs to Cherie. If we removed the clause from the sentence, the sentence’s meaning would no longer be the same.
In example four, the writer has placed commas around the relative clause which is lying on the coffee table. This clause is nonrestrictive; it is nonessential to the meaning of the sentence. We can tell by the use of the nonrestrictive clause that there is only the one book in the room, and that book belongs to Cherie. In other words, if the nonrestrictive clause was removed from the sentence, the writer’s original meaning would be preserved.
Example 5: Bob Jones, who is my next-door neighbor, won the election.
In example five, the relative clause is nonrestrictive. The fact that Bob Jones is the speaker’s neighbor has nothing to do with the intent of the sentence, and this clause could easily be removed. The clause is nonessential.
Keeping these basic points in mind will make punctuating restrictive and nonrestrictive sentences much less tricky! But if you just can’t keep it straight, give the Writer’s Relief proofreaders a call!