Commas

Here is a quick overview of the many comma rules we have to deal with.

• Use a comma before any coordinating conjunction (and, but, for, or, nor, so, yet) that links two independent clauses.

Example: “Harry went flying, and he saw a Dementor.”

An independent clause includes both a subject and verb and can stand on its own as a sentence. 

• Use a comma after a dependent clause that starts a sentence.

Example: “When Harry went flying, he saw a Dementor.”

A dependent clause contains both subject and verb but cannot stand on its own as a sentence.

Commas always follow these clauses at the start of a sentence. If a dependent clause ends the sentence, however, it no longer requires a comma. Only use a comma to separate a dependent clause at the end of a sentence for added emphasis, usually when negation occurs.

• Use commas to offset appositives from the rest of the sentence.

Appositives act as synonyms for a juxtaposed word or phrase.

Example: “While flying, Harry saw a Dementor, a being that looked like a cloaked figure.” 

“a being that looked like a cloaked figure” is the appositive. This is because it gives more information about “a Dementor.” If the appositive occurs in the middle of the sentence, both sides of the phrase need a comma. For example:

“A Dementor, a being that looked like a cloaked figure, attacked Harry.”

Don’t let the length of an appositive scare you. As long as the phrase somehow gives more information about its predecessor, you usually need a comma.

Exception to this rule: Do not offset a phrase that gives NECESSARY information to the sentence. Usually, commas surround a non-essential clause or phrase. 

Example:

“The Dementor that attacked Harry scared his friends” doesn’t require any commas. Even though the phrase “that attacked Harry” describes “the Dementor”, it provides essential information. Otherwise, no one would know why the Dementor scared Harry’s friend. Clauses that begin with “that” are usually essential to the sentence and do not require commas.

• Use commas to separate items in a series. 

Example: 

“He saw a skull, a cauldron,* and a scary cat when he entered Knockturn Alley.” 

That last comma, known as the serial comma, *Oxford comma, or Harvard comma, causes serious controversy. Although many consider it unnecessary, others, including Business Insider, insist on its use to reduce ambiguity.

• Use a comma after introductory adverbs.

“Finally, Hermione could cast a Patronus.”

“Unsurprisingly, Ron didn’t swallow before starting to talk.”

Many adverbs end in “ly” and answer the question “how?” How did someone do something? How did something happen? Adverbs that don’t end in “ly,” such as “when” or “while,” usually introduce a dependent clause. Rule number two in this post has already covered this. Phrases like “on the other hand” and “furthermore” also fall into this category.

• Use a comma when attributing quotes.

The rule for where the comma goes depends on where the attribution comes. If the attribution comes before the quote, place the comma outside the quotation marks. 

Example:The runner said, “I saw a duck.”

If attribution comes after the quote, put the comma inside the quotation marks: 

Example:“I saw a duck,” said the runner.

A detailed article on the punctuation of dialogue can be found in season 2, issue 2 of the WWN.

• Use a comma when the first word of the sentence is freestanding, for example, “yes” or “no.”

Example: “Yes, I saw a duck when I went running.” – “No, the duck didn’t bite me.”

• Use a comma when directly addressing someone or something in a sentence.

Example:Dumbledore asks, “Harry, how are you?”

• Use a comma between two adjectives that modify the same noun.

For example: “I saw the big, mean Centaur when I went running.”

Only coordinate adjectives require a comma between them. Two adjectives are coordinate if you can answer yes to both of these questions: 

1. Does the sentence still make sense if you reverse the order of the words? 

2. Does the sentence still make sense if you insert “and” between the words?

Sentences with non-coordinate adjectives, however, don’t require a comma. For example; 

“I lay under the powerful summer sun.” 

“Powerful” describes the “summer sun” as a whole phrase. This often occurs with adjunct nouns, a phrase where a noun acts as an adjective describing another noun — like “chicken soup” or “dance club.”

• Use a comma to offset negation in a sentence.

Example: “I saw a duck, not a baby seal, when I went running.”

Also use commas when any distinct shift occurs in the sentence or thought process. “The cloud looked like an animal, perhaps a baby seal.”