A comma after an introductory phrase separates it from the main clause, improving readability. This rule applies to dependent clauses, participial phrases, and other introductory elements.
Introductory phrases provide context or set the scene before the main part of the sentence. A comma after them signals a pause, helping readers process the information correctly. For example:
After finishing her homework, Sarah watched a movie. (Correct)
Without the comma, the sentence would be confusing: "After finishing her homework Sarah watched a movie." (Incorrect)
Introductory phrases can be categorized based on their structure:
Many writers omit the comma after an introductory phrase, especially in short sentences. However, even brief introductory phrases require a comma. For instance:
To be honest, I didn't enjoy the movie. (Correct)
Some writers mistakenly think that only long introductory phrases need commas. In reality, all introductory phrases-regardless of length-require a comma for clarity.
There are a few exceptions to the rule. A comma is not needed if the introductory phrase is very short and closely related to the main clause. For example:
Just then the doorbell rang. (Acceptable, though a comma would also be correct: "Just then, the doorbell rang.")
Some writers choose to omit the comma for stylistic reasons, but this can lead to ambiguity. It's generally safer to include the comma.
Another exception involves sentences starting with "therefore," which often do not require a comma. Learn more about comma usage after "therefore".
Consider this sentence without a comma:
Because she was hungry Maria ate a sandwich. (Incorrect)
The lack of a comma makes it hard to tell where the introductory phrase ends and the main clause begins. Adding a comma fixes the issue:
Because she was hungry, Maria ate a sandwich. (Correct)
By following these guidelines, you can ensure your writing is clear and easy to understand. Proper comma usage after introductory phrases is a key aspect of good writing.