Five Questions for Using Introductory Phrase Commas
During last week’s #PuncChat, one participant wondered about adding a comma after an introductory phrase. When do you need the comma? When can you drop it?
These are questions of grammar and rhythm, often addressed to varying degrees by style guides. Apply the following five questions to help you decide whether to drop the comma, your style guide notwithstanding.
1. Is the introduction really a phrase?
Many style guides give advice punctuating introductory phrases but don’t distinguish phrases from single words and clauses. Yet the rule is different for words and clauses.
Single words, generally sentence adverbs, are followed by a comma. Subordinate (dependent) clauses are followed by the comma as well:
However, you should check your style manual for its rule.
If you follow Tom’s advice, you’ll be successful.
2. Is the introduction long?
Long introductory phrases of any type need a comma after them:
Whatever the type of long introductory phrase, follow it with a comma.
Determining whether you have a long or short phrase is not an exact science. Some resources say four words; others say five. More than five is certainly a long phrase. When you have two to four words, you can use the rest of these questions to determine whether you need a comma.
3. Would omitting the comma cause a miscue?
If omitting the comma after an introductory phrase would cause a miscue, keep the comma:
Before eating, Mother always made us wash our hands.
4. Is the introductory phrase the subject of the sentence?
Read the sentence all the way through. If the phrase is the subject of the sentence, omit the comma. This is one place you might find the author has mistakenly inserted a comma, resulting in the subject being separated from its verb:
Identifying your topic is the first step in a research project.
Identifying her topic, Mary started researching earnestly.
5. Does rhythm make the comma necessary?
All of the above are grammatical reasons for keeping the comma. If none of them apply, you need to listen to the rhythm of the sentence.
Is a pause needed? Is an emphasis of what follows the introductory phrase desired? Then keep the comma.
Does the paragraph have several sentences with introductory phrases followed by commas? Drop the comma (and consider reorganizing those sentences for some variety).
The commas that follows an introductory phrase is a style rule based on grammar and rhythm. Unless your style guide says differently, use these five questions to decide whether the comma stays or goes.