Keep calm and comma on: Restrictive vs. nonrestrictive elements

by Marie Sherman

To use a comma or not to use a comma… that is the question! Well at least that’s something I often ask myself while writing. However, after reading more about commas on Writer’s Help, I have discovered some answers to share with any puzzled comma-users!

Commas are used in a variety of circumstances to break up different parts of a sentence and clarify its meaning. An important distinction to make when deciding whether or not to use a comma is in the case of word groups that describe nouns or pronouns. You must determine if the description of the noun or pronoun is necessary to the overall meaning of the sentence. If it is necessary, the description is referred to as a restrictive element. Otherwise it is an nonrestrictive element.


Because restrictive elements are the descriptions of a noun/pronouns that are essential to its meaning, they are used without commas.

Example 1: Writing tutors should ask students questions that allow them to think more deeply about the subject they are writing about.

In this sentence, the restrictive element is the description of the questions: “questions that allow [the students] to think more deeply about the subject they are writing about.” This description of the questions is essential to clarifying the meaning of the sentence, so commas are left out.

Example 2: J.K. Rowling’s book Harry Potter and the Chamber of Secrets is my favourite.

Since J.K. Rowling wrote more than one book, it is essential to clarify which book I’m talking about.

Nonrestrictive elements are the opposite because their description of nouns or pronouns is not necessary to convey the overall meaning of the sentence. Therefore, non-restrictive elements are used with commas.        

Example 1: The writing tutor helped a number of students from the same class, who all needed help on a paper. 

The students, who are described in this sentence, “all needed help on a paper.”  If you took out this description, the meaning of the sentence wouldn’t change because the tutor would still be doing the action of helping the students. The description merely provides some extra detail.

Example 2: The second Harry Potter book, Harry Potter and the Chamber of Secrets, is my favourite.

In this sentence, I have already clarified which Harry Potter book I’m talking about. Giving the title is just providing additional information.


Overall: If you are confused about whether a description of a noun/pronoun in a sentence requires commas, you can easily figure it out! Try removing the description from the sentence. If this changes the meaning of the sentence, or makes it unclear, it is a restrictive element. Don’t add commas! However, if the description doesn’t change the essence of the sentence, it is a non-restrictive element, so add commas!


Marie Sherman is a sophmore at Principia College studying education and global studies. When not writing, she is probably running around campus or dancing!

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