Comma Usage
Use commas in compound sentences, introductory elements, lists, coordinate adjectives, nonessential elements, and direct address.
A lesson of English 9, in Language, Grammar, and Vocabulary, about 10 minutes.
By the end of this lesson, you will be able to apply the major comma rules correctly and understand when commas are required, optional, or incorrect.
The Major Comma Rules
Rule 1: Before Coordinating Conjunctions in Compound Sentences
Use a comma before FANBOYS (For, And, Nor, But, Or, Yet, So) when joining two independent clauses.
"The author uses irony, but the humor is always darkly serious."
No comma if what follows the conjunction is NOT an independent clause:
"The author uses irony and darkly serious humor." (No comma — "darkly serious humor" is not a clause.)
Rule 2: After Introductory Elements
Use a comma after an introductory word, phrase, or clause.
"Although the ending is tragic, the theme survives."
"In the final chapter, the narrator realizes her mistake."
"Running out of options, Hamlet finally acts."
Rule 3: Around Nonessential Information
Nonessential (nonrestrictive) clause or phrase: adds extra information that could be removed without changing the sentence's meaning.
"Hamlet, who cannot decide, delays his revenge." — "who cannot decide" is extra; Hamlet is already identified.
Essential (restrictive) clause: cannot be removed without changing meaning. No commas.
"The character who cannot decide is Hamlet." — removing "who cannot decide" changes the meaning.
Rule 4: In a List of Three or More Items
"The essay analyzed setting, characterization, and theme."
The Oxford (serial) comma before the last item is recommended for clarity.
Rule 5: Separating Coordinate Adjectives
When two adjectives equally and independently describe a noun, separate them with a comma.
"It was a cold, dark night." (Both cold and dark modify "night" independently — cold, dark night; dark, cold night.)
No comma if the first adjective modifies the combination of the second adjective + noun:
"It was a cold winter night." (Not "winter, cold night" — these aren't coordinate.)
Test: if "and" works between the adjectives, use a comma. "Cold and dark night" — yes. "Cold and winter night" — awkward.
Common Comma Mistakes
Comma splice: "The play ends in tragedy, the audience is left with questions."
Two independent clauses joined with only a comma. Fix with a period, semicolon, or conjunction.