Tiny Grammar Cheatsheet: Oxford Comma
actually called “serial comma” but now known as oxford comma since Oxford University Press famously uses it
used before conjunctions (and, or, nor, …) in a list
separates the final two items in a list and clarifies meaning: “He reads romance, historical fiction and nonfiction.” ← does he read all three genres separately or does he read romance + both historical fiction and historical nonfiction? → “He reads romance, historical fiction, and nonfiction.”
clears up ambiguity: “We invited the neighbors, Agatha and Christie.” vs. “We invited the neighbors, Agatha, and Christie.”
can also create ambiguity: “She talked with John, his dad, and Mary.” ← is John someone's dad or did she talk with John's dad?
(In both cases, ambiguity could also be avoided by changing the sentence structure: “We invited Agatha, Christie and the neighbors.” & “She talked with John, Mary, and his dad.”)
Should you use the Oxford Comma? There is no correct choice. Even though some have extremely strong opinions on the oxford comma, neither is typically seen as incorrect or correct. Whatever you choose to do, just do it consistently, meaning use it in every list or in no list to avoid accidentally creating new ambiguity.
