Use a comma to set off introductory word,phrases,and clauses from the main part of a sentence. The comma keeps a reader from accidentally attaching the introductory portion to the main part of the sentence and having to go back and reread the sentence. In other words, commas following introductory elements will save the reader time and reduce the chances of misinterpreting what you write.Examine the following examples to see how introductory words, phrases,and clauses are set off with commas.