A relative clause is a word, clause, or phrase that modifies some element of the main clause. Relative clauses are introduced by relative pronouns. Common relative pronouns include who/whom, whoever/whomever, whose, that, and which. In general, they come in two types: non-restrictive and restrictive., Non-restrictive modifiers are relative clauses or phrases that add information to a sentence but aren’t essential to the meaning of the sentence. If you removed a non-restrictive modifier from the sentence, it would still make sense (and the main subject of the sentence would still be in place). They are also sometimes called “interrupters.”Here is an example of a non-restrictive modifier in a sentence: “George Washington, our first president, served two terms.” While the information in the non-restrictive modifier is helpful, the main clause makes sense if it’s removed: “George Washington served two terms.”
Here is another example of a non-restrictive modifier: “Fatima, who has been studying hard, will probably do well on today’s exam.” The presence of who (a relative pronoun) in a clause is often a sign that it’s non-restrictive and should be set off by commas.
 In almost all cases, non-restrictive clauses or phrases will be set off on both sides by commas. This indicates to the reader that they’re additional information, but not necessarily essential. If you can remove the clause without damaging the sense of your sentence, it is almost certainly a non-restrictive modifier.


Make sure to set off the entire modifier with commas, using one at each end. A common comma error is to set off the beginning of the modifier with a comma, but not the end.
In almost all cases, relative clauses or phrases beginning with which will be non-restrictive modifiers and should be set off with commas: “The car accident, which occurred at 3 PM, didn’t damage my car too badly.”

, Sometimes, prepositional phrases and other phrases interrupt the main sentence, serving as non-restrictive modifiers. If these interruptions are separate from the main subject and verb, separate the interruption phrase with commas to signal to the reader that this information is inessential.


For example, here is an example of a prepositional phrase acting as an interrupter: “It is, in my opinion, an excellent book.” This phrase isn’t crucial to the meaning, and can be taken out without damage to the sentence.
Here is another example: “This road, on the other hand, is well-paved and easy to drive.”
Direct address also falls into this category. For example, here is a sentence interrupted by a direct address to another person: “That's why I'm appointing you, Thomas, leader of the group.”

, Restrictive modifiers are relative clauses or phrases that are crucial to the meaning of your sentence. They cannot be removed without damaging the sense of your sentence.


Here is an example of a restrictive modifier in a sentence: “Drivers who exceed the speed limit are reckless.” This clause is essential to the meaning of the sentence and cannot be removed.
Here is another example of a restrictive modifier: “The song named “Roar" is popular; the song named “Latte Love" that I made up yesterday is not.’’ While these modifiers do offer additional information, they cannot be removed without obliterating the sentence’s meaning: “The song is popular; the song that I made up yesterday is not.”

, Because they are essential to the meaning of your sentence, setting off these clauses or phrases with commas will interfere with the clarity of your sentence.


In almost all cases, a clause beginning with the relative pronoun that will be restrictive and should not be set off with commas: “The car accident that I had yesterday will really raise my insurance bill.”
Understand what a relative clause is.
Understand how non-restrictive modifiers work.
Use commas with non-restrictive modifiers.
Use commas to offset expressions that interrupt the sentence.
Understand how restrictive modifiers work.
Avoid using commas with restrictive modifiers.
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