When you have introductory material that comes before the main subject of the sentence, you probably need to set that introductory information off with a comma. The introductory material can be in the form of words, phraes, or clauses. I'll list some examples below:

After he made the shot, Mr. Green smiled broadly.

Because the timelines were due at the end of the period, all the students worked diligently.

Although he faced challenging witnesses, Alex brought the truth to light through careful questioning.

Until Darren gave his brilliant defense of Odysseus, many students planned to vote for a guilty verdict.

Wishing she could convince everyone of Odysseus' innocence, Kirke gave a passionate and moving speech.

Looking for a different challenge, some students chose the poetry assignment.

Under the table in the front of the room, Athena found Hermes magic sandals.

To prepare for his speech, Melantho practiced rotating his severed head.

The Gregg Reference Manual recommends the use of a comma after all introductory prepositional phrases, unless the phrase is short and leaving the comma out doesn't make the sentence confusing. For example, "In May we will study Romeo and Juliet." You may omit the comma after the short prepositional phrase "In May."

Also, be careful of sentences where the introductory phrase is actually the subject of the sentence. In that case, you would not use a comma. For example, "Reading the entire Odyssey is the best way to understand it." In that sentence, "Reading the entire Odyssey" is the subject of the sentence.

Also watch out for sentences with inverted word order. You don't need a comma afer introductory material if the word order in the sentence is inverted. For example, "After hearing from all the students involved make up his mind the teacher did.

Not so long ago, you completed some exercises involving commas in compound sentences. We talked about how a compound sentence requires a comma before the conjunction. When you come across a compound sentence, you have to treat each clause as a separate sentence. So, if the second clause in a compound sentence begins with an introductory phrase or clause, you must use a comma to set off the introductory material. Got that? For example, let's take the compound sentence: Michael Jordan will play in the All Star game this afternoon, but he will not start. Now lets add a little introductory material to the second part of the compound sentence: Michael Jordan will play in the All Star game this afternoon, but for the first time in his career, he will not start. The prepositional phrase, "for the first time in his career" serves as introductory material for the second clause in the compound sentence.

Now you can try some exercises. (Please note: afer you finish each set of sentences, you'll need to use your browser's back key to get back to this page.)