Comma after prepositional phrase at beginning of sentence

An introductory phrase is a short clause that starts a sentence. It doesn’t have its own subject and verb. Instead, it uses the main clause’s subject and verb. Introductory phrases help to set the stage for the main part of the sentence. They let the reader know that the central message of the sentence is coming.

Introductory clause: After the food was finished, the girl was still hungry. 

Introductory phrase: While washing the dishes, he heard the baby cry.

There are different kinds of introductory phrases, such as prepositional phrases and appositive phrases. Some introductory phrases need a comma. In some situations, using a comma is optional. And, sometimes, it’s wrong to use a comma. 

The first rule is that you should always use a comma if the sentence could be misinterpreted otherwise.

Commas with Introductory Prepositional Phrases

If an introductory prepositional phrase contains four or more words, then it needs a comma. If it is shorter, then a comma is optional. 

Here are some helpful examples:

Prepositional phrases with less than four words:

Correct: Before summer I’ll lose some weight.

Correct:Before summer, I’ll lose some weight.

Prepositional phrases of more than four words:

Correct: After circling the block twice, Jaclyn was ready to park anywhere.

If the introductory phrase contains two prepositional phrases, you need to use a comma. The introductory phrase below includes two prepositional phrases: “during the snowstorm” and “in February.”

Incorrect: During the snowstorm in February all the plants died.

Correct: During the snowstorm in February, all the plants died.

Commas with Restrictive Appositive Phrases

Appositive phrases rename the subject of a sentence. For example, “the overachiever” is an appositive phrase to refer to Joseph:

Example: Joseph, the overachiever, always had perfect grades.

There are restrictive and nonrestrictive appositive phrases. A restrictive appositive phrase is necessary to the sentence’s meaning. Commas are not used with restrictive appositive phrases.

A nonrestrictive appositive phrase adds information to the sentence but isn’t necessary to the meaning. The example above shows a nonrestrictive appositive phrase because the sentence makes sense without it. Here is an example of a restrictive appositive phrase:

Example: The race car driver Jeff Gordon is my favorite.

This appositive is restrictive because it is necessary for the reader to know which race care driver they are referring to. Sometimes, a restrictive appositive phrase acts as an introductory phrase. When that happens, don’t use a comma to separate the phrase from the subject.

Incorrect: The best-selling author, Mr. Brian Rockhold, did a reading at the bookstore.

Correct: The best-selling author Mr. Brian Rockhold did a reading at the bookstore.

Learning all the rules about commas with introductory phrases may be challenging at first, but it gets easier with practice.

Related: Test your punctuation prowess with this test. 

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A comma may also set off a single prepositional phrase at the beginning to make the sentence clear. A comma is recommended after any introductory prepositional phrase of more than four words.

Correct: Under the kitchen table the dog cowered.
(Single short, clear phrase. No comma needed.)

Correct: Under the spreading chestnut tree, the village smithy stands.
(Comma optional, but helpful due to length of phrase)

Correct: Under the pile of clothes, we found his wallet.
(Two prepositional phrases, not in a series)

Incorrect: On the sand, of the beach, by the inlet, we relaxed in the sun.
(Do not separate the phrases since they are not in a series.)

Correct: On the sand of the beach by the inlet, we relaxed in the sun.

Correct: Over hill, over dale, we hit the dusty trail.
(The two phrases are in series here. We could say "Over hill and over dale.")

Correct: Looking for help, the man fell on his knees to beg.
(Participial phrase)

Correct: To raise enough money in time, Mary had to issue stock in her business.
(The infinitive phrase is used as a modifier)

Incorrect: To ski, is exhilarating.
(The infinitive is used as a noun, not a modifier.)

Correct: To ski is exhilarating.

Can you start a sentence with a prepositional phrase?

Do you put commas before or after prepositional phrases?

When to put a comma at the beginning of a sentence?