Commas, Introductory

Introductory commas come between an initial word, phrase, or dependent clause and the main (independent) clause of a sentence. Their purpose is to signal the end of this introductory material and the arrival of the main subject and verb, helping readers to parse your syntax accurately on the first read.

To identify whether a sentence needs an introductory comma, locate the main subject—the one in the independent clause of your sentence—plus any modifiers appended to it. If any material precedes this main subject, insert a comma:

• In the wake of the decisive naval engagement at Dan-no-ura, the victorious Minamoto clan established Japan’s first shogunate.

(In a sentence with multiple independent clauses, this comma will instead be a FANBOYS comma or a colon or semicolon.)

Note that a sentence can have more than one distinct introductory word, phrase, or clause; in such cases, place a comma after each.

Introductory Commas Practice Exercises

Which sentences need introductory commas? Where?

1. If it is raining spaghetti will be served.
2. Even if you have a dog a cat or a parrot is a nice addition to your menagerie.
3. Whether the agreement will remain in effect will depend to a large extent on the testimonies next week.
4. Import prices will likely continue to rise whether or not the agreement remains in effect.
5. In 1815 however Napoleon abdicated following his defeat at the Battle of Waterloo.
6. In 1815 however Napoleon had prepared for the encounter he was defeated by Wellington.

Answers

1. If it is raining, spaghetti will be served. ("Spaghetti” is the main subject; without the comma, we might initially think it could rain spaghetti.)
    
2. Even if you have a dog, a cat or a parrot is a nice addition to your menagerie. (“A cat or a parrot” is the main subject; with no comma, we might read the beginning as an unpunctuated list of three animals you might already have. Even with the intro comma, it could still sound like a list at first, which is a good argument for consistently employing the serial comma.)
    
3. No intro comma needed: “Whether the agreement will remain in effect” is the main subject here, followed by the main verb, “will depend”; there is no introductory material before the main subject. Compare this sentence, in which the “whether” is part of an introductory dependent clause: “Whether or not the agreement remains in effect, import prices will likely to continue to rise.”
    
4. No intro comma needed, as the independent clause comes first.
    
5. In 1815, however, Napoleon abdicated following his defeat at the Battle of Waterloo. (“In 1815” and “however” are discrete introductory particles—one indicating time, one indicating tension or contradiction; each, therefore, gets its own introductory comma.)
    
6. In 1815, however Napoleon had prepared for the encounter, he was defeated by Wellington. (“In 1815” still gets its introductory comma, but, this time, “however” introduces a long dependent clause; we don’t arrive at the main subject and verb until “he was defeated.”)
    

Further Practice and Other Introductory Comma Links

• GWC writing mechanics module: Commas
• Video (3:05): "Using a comma after an introductory element," Georgia State University
• Handout (printable): "Commas and Introductory Elements," Connecticut Community College
• Webpage: "Commas," University of North Carolina Chapel Hill
• Exercises: "Commas and introductory elements," Khan Academy