How to Punctuate Introductory Prepositional Phrases

Or when and when not to follow an introductory prepositional phrase with a comma

Photo by Marvin Kuhn on Unsplash

In the English language, it’s common for a sentence to begin with an introductory phrase or clause. If such an introduction is a clause, it will contain a subject and a verb. Since the introduction of the first sentence of this post (“In the English language”) doesn’t include a verb, you know right away that it’s an introductory phrase rather than an introductory clause. An easy way to remember the difference is to keep in mind that a clause always contains a verb, and “clause” and “contains” both start with the letter “c.”

As far as introductory phrases go, many are prepositional phrases. Prepositional phrases contain, at the very least, a preposition and the object of that preposition. In my intro to this post, “In the English language,” “in” is a preposition and “the English language” is its object.

I state in my post “Different Types of Prepositions and the Extra Words None of Them Need” that prepositions usually indicate where and when. Common prepositions include “after,” “before,” “during,” “above,” “across,” “among,” “around,” “at,” “behind,” “below,” “between,” “by,” “down,” “from,” “in,” “into,” “on,” “out,” “over,” “through,” “to,” “under,” “up,” “with,” and “without.”

Writers often begin sentences with prepositional phrases. Examples of introductory prepositional phrases include “between you and me,” “over time,” “without a second thought,” “around noon,” “across town,” “at last,” and “by the way.” Longer prepositional phrases can include more than one prepositional phrase as in “After midday but before it got too hot.”

To punctuate or not to punctuate

The general rule related to using commas after introductory prepositional phrases has to do with the number of words in the phrase. If an introductory prepositional phrase contains fewer than four words, a comma is not necessary but is also fine to use. “At the market they bought croissants,” for example, is correct, but so is “At the market, they bought croissants.” Feel free to go with the option you prefer.

When an introductory prepositional phrase contains four or more words, however, or when more than one prepositional phrase is used together at the start of a sentence, a comma is necessary. Consider this example: “After midday but before it got too hot, they went to the market and bought croissants.”

Easy enough, but what if a prepositional phrase appears at the end of a sentence? In general, no comma is needed before a prepositional phrase of any length when it appears at the end of a sentence, as in: “They went to the market and bought croissants after midday but before it got too hot.”

Key takeaways

• Many sentences start with a clause or phrase, including prepositional phrases.

• A comma after an introductory prepositional phrase is optional if the phrase has fewer than four words.

• A comma is needed when an introductory prepositional phrase has four or more words or includes a second prepositional phrase.

• Prepositional phrases at the end of a sentence generally don’t need to be preceded by a comma.

An earlier version of this post appeared in The Writing Cooperative.

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I write fiction, poetry, and nonfiction when I’m not working as a copy editor. Author of the novel One Sister’s Song and the e-book Not Nearly Everything You Need to Know About Writing.