As an editor, you are expected to know all of the basic comma rules listed in the Purdue Comma Guide. Beyond the basics, these are the comma rules you should be most aware of.
- DO use commas when they are needed (because they add clarity and separate elements of a sentence).
- DO use a comma after introductory clauses and phrases.
- DO use a comma to separate independent clauses when they are joined by a coordinating conjunction.
- DO use a comma to set off non-essential elements of a sentence (a non-essential element is a phrase, clause, or group of words that can be removed without changing the meaning of a sentence).
- DO NOT overuse commas (by adding a comma every time you feel a pause is needed).
- DO NOT use a comma to set off essential elements of a sentence (an essential element is a phrase, clause, or group of words that can’t be removed from a sentence without changing the sentence’s meaning).
- DO NOT use a comma around phrases that start with “that” (they are always essential).
- DO NOT use a comma between two nouns, noun phrases, or noun clauses in a compound subject.
- DO NOT use a comma between two verbs or verb phrases in a compound predicate.
- DO use a serial/Oxford/Harvard comma in a series.
Use a comma to separate three or more words, phrases, or clauses in a series. Include a serial/Oxford/Harvard comma (a comma before the conjunction) unless otherwise stated in a style guide. (*This is a CopyPress standard that we use for clarity in online content.)