Do You Need a Comma Before or After a Prepositional Phrase?

Comma rules are one of the trickiest parts of English grammar to understand, especially combined with other grammar rules like prepositional phrases.

So, do you need to use a comma after a prepositional phrase? What about before a prepositional phrase?

A comma is optional after a short prepositional phrase, but you should always use a comma after an introductory prepositional phrase that has more than four words. If the prepositional phrase comes in the middle of the sentence, you don’t need to include a comma before it.

Read on to learn how to use commas correctly with prepositional phrases.

What Is a Prepositional Phrase?

A prepositional phrase is a phrase that starts with a preposition, which is a word that shows direction, time, place, or some other important relationship.

Some common prepositions include after, before, from, and on, among many others.

Here are some examples of prepositional phrases that use those prepositions:

• After I finish my homework

• Before she got to the restaurant

• From dusk until dawn

• On top of the kitchen counter

Many sentences include an introductory prepositional phrase at the beginning. Introductory prepositional phrases set the scene for the rest of the sentence.

For example, this sentence has an introductory phrase: “After I finish my homework, I can watch a movie with you.”

Not all prepositional phrases are introductory phrases. You might also find prepositional phrases in the middle of a sentence or at the end of a sentence.

For example, this sentence has a prepositional phrase in the middle: “I’m very busy, but after I finish my homework, I can watch a movie with you.”

A prepositional phrase is different from an appositive phrase, which is a noun that redefines another noun, such as in the sentence "My sister, Sandy, has two dogs."

With an introductory appositive phrase, you only need to use a comma if it's a nonrestrictive appositive phrase, meaning that the phrase isn’t necessary for the reader to understand the central message of the main clause. If it's a restrictive appositive phrase, you don't need to use a comma.

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Do You Need a Comma After a Prepositional Phrase?

For short introductory phrases (one that has fewer than five words), you can choose to add a comma or not.

For longer phrases that have more than four words, you should always use a comma.

Here’s an example of a short introductory prepositional phrase, which works with or without a comma.

Correct: In the morning let’s go to the zoo.

Correct: In the morning, let’s go to the zoo.

And here’s an example of a longer prepositional phrase, which requires the comma.

Incorrect: On the morning of his birthday Robbie wanted to go to the zoo.

Correct: On the morning of his birthday, Robbie wanted to go to the zoo.

Do You Need a Comma Before a Prepositional Phrase?

With introductory prepositional phrases, you obviously don’t need to use a comma before them since there’s nowhere to put the comma.

But what about when the prepositional phrase comes in the middle of a sentence?

For example, consider the sentence, “He went to bed, and after he woke up, he felt much better than before.”

In this scenario, you don’t need to include a comma before the prepositional phrase.

This example is a compound-complex sentence, meaning it contains two independent clauses and one dependent clause (“after he woke up”). In a compound-complex sentence, you can just attach the prepositional phrase directly to the conjunction that comes before it (“and”).

Here’s another example.

Incorrect: She loves to eat ice cream, but, when she talked to the doctor yesterday, she found out she’s lactose intolerant.

Correct: She loves to eat ice cream, but when she talked to the doctor yesterday, she found out she’s lactose intolerant.

Examples of Commas Before and After Prepositional Phrases

Here are some more examples of how to use commas with prepositional phrases.

Correct: Under that tree there’s a cute little raccoon.

Correct: Under that tree, there’s a cute little raccoon.

Incorrect: Before you go to the party you need to finish all your homework.

Correct: Before you go to the party, you need to finish all your homework.

Incorrect: Inside that big filing cabinet over there you’ll find the papers you’re looking for.

Correct: Inside that big filing cabinet over there, you’ll find the papers you’re looking for.

Incorrect: I’m not supposed to tell you this yet, but, between you and me we all loved your performance yesterday.

Correct: I’m not supposed to tell you this yet, but between you and me, we all loved your performance yesterday.

Incorrect: Someone’s standing, behind you.

Correct: Someone’s standing behind you.

Incorrect: I think there’s an impostor, among the seven of us.

Correct: I think there’s an impostor among the seven of us.

Incorrect: I was minding my own business, and, out of the blue she just started yelling at me.

Correct: I was minding my own business, and out of the blue, she just started yelling at me.

How ProWritingAid Can Help You Use Commas Correctly

If you’re not sure you’re using commas in the right places, you can run your writing through ProWritingAid. Our free grammar checker will highlight any punctuation errors and help you fix them with one click.

Good luck, and happy writing!