Use a complete sentence to explain when an introductory prepositional phrase should be followed by a comma and when it should not.

When to Use Commas After Restrictive Appositive Phrases

When the introductory phrase is a restrictive appositive phrase, don’t use a comma to separate it from the main clause. An appositive phrase is a phrase that renames the subject of the sentence. For example, the highlighted phrase in the sentence below is an appositive phrase because it renames the subject:

Example: Kate, an only child , demands a lot of attention.

There are two types of appositive phrases: restrictive and nonrestrictive. A restrictive appositive phrase is one that is necessary to the meaning of the sentence. A nonrestrictive appositive phrase isn’t necessary but simply adds information to the sentence. The example appositive phrase above is nonrestrictive because the sentence still makes sense without the phrase; it just doesn’t include as much information. The sentence below, however, contains a restrictive appositive:

The opera singer Maria Callas had myopia.

In this case, the appositive is restrictive because it is necessary for the reader to know which opera singer had myopia. Sometimes, a restrictive appositive phrase acts as an introductory phrase. In these instances, don’t use a comma to separate the phrase from the subject that it renames.

The award-winning teacher, Mrs. Becky Armstrong, was honored at graduation for her impact on students’ lives.

The award-winning teacher Mrs. Becky Armstrong was honored at graduation for her impact on students’ lives.