Commas Part 2: Introductory Elements

When we write, we don’t always start our sentences with the subject: I graduated from college five years ago.

We often — and we should — vary our sentence structure, beginning with an introductory word, idiom, phrase (group of related words), or clause (group of related words with a subject and a verb).  Many of these introductory elements are followed by a comma.

Introductory Words

Most of the time introductory words are transitional words like first, second, next, last, finally, etc. Transition words are generally followed by a comma.

• First, I would like to introduce our guest speaker.
• Finally, you should always check your work.

Sometimes a sentence begins with an adverb. We have a gray area here. Sometimes there is a comma, and sometimes there isn’t. In this case, the “pause” test works. If you think there should be a pause there, put in a comma.

• Obviously, I hid the surprise from her.
• Suddenly she appeared at my doorway.

Introductory Phrases

There are several types of phrases. You can begin a sentence with a prepositional phrase. If the phrase is short, you do not need a comma after it. However, if it is longer, or if you are using two prepositional phrases in a row (or two consecutive phrases of different types), you probably need a comma.

• In Paris I bought myself an entirely new wardrobe.
• In Paris in December, you probably need a heavy coat.

You can also begin a sentence with a participle or a participial phrase. Usually a comma follows a participial phrase.

• Walking along the river, she spotted a lost dog.
• Walking quickly, she tried not to miss the bus. 

Make sure your participial phrase isn’t misplaced or dangling. The word following the comma should go with the phrase. Here are a couple of misplaced modifiers:

• Walking along the river, the rain began to come down. (Is the rain walking along the river??)
• Reading a book by the window, the cat jumped in my lap. (Is the cat reading a book by the window??)

Be careful with your participles!

Descriptive phrases are usually followed by a comma.

• Pretty as a picture, she walked down the fashion runway.

Here are some examples of phrases that would not be followed by a comma.

Infinitives look like verbs with the word to in front of them. But they are not verbs. They are actually used as nouns. Therefore, they themselves can be the subjects, so technically the subject is starting the sentence.

• To become a doctor is my ambition. (No comma after doctor. To become a doctor is used as a noun and is the subject.)

Gerunds also look like verbs — or participles — but again they are used as nouns and can actually be the subject.

• Skiing  in Tahoe is my favorite hobby.
• Running a few miles is something I try to do every day.

Introductory Sayings or Idioms

Once again, this is sometimes a gray area. Usually, there is a comma after an introductory idiom, but not always. Once again, the “pause” test usually works!

• In my opinion, this is not the right way to do it. 
• Of course, I am not an expert on the subject.
• Of course I will go with you.

Introductory Clauses

Introductory adverbial clauses are always followed by a comma. Those clauses begin with words such as although, until, before, after, since, because, whenever, wherever.

• Although I wasn’t there, I heard about what went on.
• After the game is over, we are going out to dinner.
• Because I have a doctor’s appointment, I will miss school tomorrow.

Introductory noun clauses are usually not followed by a comma (and there would be no pause) because they are subjects.

• Whoever is coming should RSVP to me. 
• Whatever you tell me will be kept secret.
• Whatever you tell me, I will keep secret. (Here, I is the subject, not the introductory clause. You would probably want to put a comma there.)