Should an introductory phrase be followed by a comma?

An introductory comma should be used following a dependent introductory phrase or clause. A dependent introductory phrase or clause is a set of words that appears before the main body of a sentence. They prepare your reader for what the rest of the sentence will be about.

Introductory clauses that need an introductory comma include those that start with adverbs like after, although, as, because, before, if, since, though, until, when, etc.

• If you want to win, you must practice every day.
• Because she begged insistently, I gave the little dog a treat.

Introductory phrases are not complete sentences. They don't contain a subject and a verb. Rather, they include prepositional phrases, appositive phrases, participle phrases, infinitive phrases, and absolute phrases.

Always use a comma after an introductory phrase or clause to help readers avoid confusion.

• After adjusting for inflation, real wages decreased across the board.
• Since he was a popular and well-respected mayor, George felt he had a shot at governor.