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If you read "Bob, a DJ and a clown" on a guest list, are three people coming to the party, or only one? That depends on whether you're for or against the Oxford comma perhaps the most hotly contested punctuation mark of all time. When do we use one? Can it really be optional, or is there a universal rule? TEDEd explores both sides of this comma conundrum.

Lesson by TEDEd, animation by Zedem Media.