Introductory Prepositional Phrases

Why should you put a comma after prepositional phrases?

An introductory prepositional phrase sets the scene for the main phrase. It is often to do with time or location, e.g. In the evening or In 2022. An introductory prepositional phrase starts with a preposition (words like in, on, after, before). For short introductory phrases (fewer than four words), you can choose to add a comma or not. For longer phrases, you should always use a comma.

Short prepositional phrase:

• Correct: In the Spring let’s go to Mexico.

• Correct: In the Spring, let’s go to Mexico.

Longer phrase:

• Correct: On the first day of his holiday, Jimmy wanted to go sailing.

• Incorrect: On the first day of his holiday Jimmy wanted to go sailing.

Note: you might also find these prepositional phrases in the middle of sentences after a conjunction, e.g. He went to bed, and in the morning, he wanted to go sailing. For these, you should follow the same rules as if they came at the beginning of a sentence.