When to Use a Comma Before “Or”

You may have noticed that people often use a comma before the word “or”. Then again, in some situations, they don’t. Today, we’ll lay out the rules for using commas with the word “or,” and, luckily, those rules are simple. There are only two main circumstances when you’ll need to remember to use commas. 

First, you always need a comma when you use the word “or” as a coordinating conjunction and place it between two independent clauses. Next, depending on the style guide you use, you may need to place a serial comma, also called an Oxford comma, before the word “or” when it’s used in a list. Other than that, try to follow the normal rules for using commas. If you can’t quite remember the rules, we’ve included a refresher at the end of this article.

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Coordinating Conjunctions

When you want to join two independent clauses, you can either use a coordinating conjunction or a semicolon. Try to memorize FANBOYS, the mnemonic device to help you remember the coordinating conjunctions. 

F – For

A – And

N – Nor

B – But

O – Or

Y – Yet

S – So

Imagine you have two independent clauses:

I wanted pie. 

I wanted nothing at all. 

You know that the clauses above are independent, not dependent, clauses because they each stand alone as a complete sentence. If you want to join them together in a compound sentence, you could write the first independent clause, use a comma and a coordinating conjunction, then include the second independent clause at the end of the sentence. 

I wanted pie, or I wanted nothing at all. 

Now, imagine the above example without the second subject and verb. If you didn’t include the second independent clause in its entirety, you would not need a comma before the word “or” and the rest of the sentence. 

I wanted pie or nothing at all. 

Although the two italicized sentences above look very similar, only one of them features two independent clauses joined by a coordinating conjunction. Therefore, only the first sentence requires a comma before the word “or”. 

Serial Commas

When writing in the English language, authors must make some stylistic choices. For example, comma usage can sometimes be a matter of opinion rather than proper use. Some grammar guides recommend a serial comma, and others don’t. As a writer, you will have to decide whether to include a comma before “and” and “or” in a list. 

Let’s look at a standard list of items:

I need books, papers, pencils, and crayons. 

The comma before the word “and” in the sentence above is known as a serial comma. It’s also called an Oxford comma and a Harvard comma. That comma could be removed without changing the meaning of the sentence. 

I need books, papers, pencils and crayons.

Some style guides suggest using the extra punctuation mark, while others contend that the sentence works better without the last comma. A writer should make a decision about whether to use serial commas before the last item in a list, and then he or she should stick to that decision within a single composition. To avoid misreading, serial commas can be particularly useful in long, complicated lists. 

She couldn’t decide whether to play the harp, ski down the mountain, or entertain her guests. 

The comma before “or” in the sentence above is considered optional; however, if you’ve already introduced the use of a serial comma in the same piece of writing, you must continue to use it. Writers should remain consistent within a single work.

Other Grammar Rules

Now that we’ve covered the two main scenarios where you may need to introduce commas before the word “or,” we can move on to some of the general rules for comma usage. Some of these rules will not be relevant to the word “or,” but other rules do apply.

Avoid Comma Splices

Never separate two independent clauses with just a comma. As mentioned above, you can only separate two independent clauses with a comma and a coordinating conjunction or with a semicolon. 

I wanted pie; I wanted nothing at all.

Set Off an Introductory Phrase With a Comma

If a sentence begins with a prepositional phrase of more than four words, you should follow the phrase with a comma. The same rule holds true when a sentence begins with an introductory word or phrase or a transitional word or phrase. As it happens, this rule does not impact the word “or,” since you wouldn’t follow a prepositional phrase, introductory phrase, introductory adverb, or transition with a conjunction. 

Interestingly, he arrived 30 seconds after I did. 

Set Off an Appositive With a Pair of Commas

An appositive follows a noun and renames it. You may use the word “or” in this context, as it may introduce a synonym or another name for the noun. This use of a comma and an appositive is especially common for translations. 

Mi casa, or my house, has three rooms. 

Set Off an Inessential Clause With a Pair of Commas

Sometimes a sentence includes a parenthetical or inessential clause. If you can remove the information without changing the meaning of the sentence, the clause should be separated from the main clause with commas. Typically, the word “or” will not introduce an inessential clause. When it does, the question should probably be marked off with em dashes for added clarity. 

She wandered through the backyard—or was it the front yard?—before getting into the car. 

In the sentence above, the question in the middle does not contain essential information. It could just as easily be removed from the sentence or placed inside parentheses. Since it’s not an essential clause, most writers would place the question between dashes or commas.

Commas in Dialogue

Writers often use commas to punctuate in and around dialogue that appears in quotation marks. The word “or” is not typically used in attribution for dialogue. When the word “or” is used within a quotation, it is unlikely to appear in a part of the sentence that requires special punctuation. 

“Are you hungry?”

“I’m a little bit hungry, or I could eat later,” he answered. 

Use Commas With Coordinate Adjectives

Coordinate adjectives require a comma; however, you would not encounter the word “or” used in this context. 

She’s a clever, charismatic student. 

Sources:

  1. https://www.businessinsider.com/a-guide-to-proper-comma-use-2013-9
  2. https://owl.purdue.edu/owl/general_writing/punctuation/commas/extended_rules_for_commas.html
  3. https://style.mla.org/serial-commas-and-semicolons/