He has plundered our seas, ravaged our coasts, burnt our towns, and destroyed the lives of our people.

—Declaration of Independence

You may see a series with no comma after the next-to-last item, particularly in newspaper writing. Occasionally, however, omitting the comma can cause confusion.

Without the comma after peas, you wouldn’t know if there were three choices (the third being a mixture of peas and carrots) or four.

Coordinate adjectives—two or more adjectives that relate equally to the noun they modify—should be separated by commas.

In a sentence like The cracked bathroom mirror reflected his face, however, cracked and bathroom are not coordinate because bathroom mirror is the equivalent of a single word, which is modified by cracked. Hence, they are not separated by commas.

You can usually determine whether adjectives are coordinate by inserting and between them. If the sentence makes sense with the and, the adjectives are coordinate and should be separated by commas.

They are sincere and talented and inquisitive researchers.

The sentence makes sense with the ands, so the adjectives should be separated by commas: They are sincere, talented, inquisitive researchers.

The sentence does not make sense with and, so the adjectives elegant and pocket should not be separated by a comma: Byron carried an elegant pocket watch.