There are 7 essential comma rules to learn. Learn when to use them, when not to use them, and how to avoid comma errors.

7 Comma Rules

Comma Rule #1: Use a comma after the penultimate item in a list of three or more items, before “and” or “or” (e.g. an Italian painter, sculptor, and architect).

INCORRECT: Da Vinci was an Italian painter, sculptor and architect.

CORRECT: Da Vinci was an Italian painter, sculptor, and architect.

Comma Rule #2: Use a comma to separate a prepositional phrase from the main sentence.

INCORRECT: In my office everyone has their own little cubicle.

CORRECT: In my office, everyone has their own little cubicle.Prepositions: in, at, on, to, by, for, etc.

Comma Rule #3: Use a comma to separate an adverb from the main sentence.

INCORRECT: Suddenly a chill went down my spine.

CORRECT: Suddenly, a chill went down my spine.Adverbs: suddenly, all of a sudden, silently, quickly, angrily, fortunately, unluckily, etc.

Comma Rule #4: Use a comma after time clauses that introduce sentences.

INCORRECT: After I got home I went straight to bed.

CORRECT: After I got home, I went straight to bed.Time clauses: After I got home, when I saw her, once I realized the time, etc.

Comma Rule #5: Use a comma after introductory phrases.

INCORRECT: In the morning I go for a jog.

CORRECT: In the morning, I go for a jog.

Comma Rule #6: Isolate interruptions with commas. 

INCORRECT: It would in turn lead to better health for people living in cities.

CORRECT: It would, in turn, lead to better health for people living in cities.

Comma Rule #7: Use a comma to separate two independent clauses joined by a conjunction.

INCORRECT: The people on the boat were laughing and the people on the beach were watching. (Run-on sentence error)

CORRECT: The people on the boat were laughing, and the people on the beach were watching.Conjunctions: and, but, or, so.

BE CAREFUL: Don’t put a comma before an “and” + verb without a subject.

INCORRECT: The people on the boat laughed, and sang.

CORRECT: The people on the boat laughed and sang.

Comma Rule #8: Do not join two sentences with a comma. This is called a comma splice.

INCORRECT: It was getting late, I was starting to panic.

CORRECT: It was getting late, and I was starting to panic.

CORRECT: It was getting late. I was starting to panic.

Comma Practice Exercises