When To Use A Comma Before “Or”

“Or” is a versatile word that provides an audience with a choice between multiple ideas, actions, or items. It can be used before an independent clause or introduce a subordinate clause. It also can be used to list items.

When using “or” in a sentence, you may have seen it used with a comma, but do you know when comma usage is appropriate with its use?

We have provided a quick guide below to help you understand these simple rules and to help keep your writing as clear and concise as possible.

What Part of Speech Is “Or”?

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“Or” is used to link alternatives in a sentence together. It introduces an air of critical thinking and requires the reader to consider more than one answer.

It also has more than one part of speech.

“Or” is most commonly used as a coordinating conjunction to link two independent clauses. But “or” can also be a subordinating conjunction to introduce a subordinate clause.

For example:

  • Did the class period end on time last Friday, or was the class period delayed due to the pep rally?
  • I’m going to leave Tuesday night or whenever it stops raining, whichever comes first.

Or can also be used to separate items in a list.

For example:

  • I’m either leaving Tuesday night, Wednesday morning, or Wednesday afternoon.
  • You need to choose between pizza or fried chicken for dinner.

Using a Comma Before “Or”

There are a few instances in which you will use a comma either before “or” or after it. These are simple instructions that follow the basic rules for comma usage pertaining to proper grammatical elements and sentence structure.

Using “Or” as a Coordinating Conjunction

An independent clause expresses a complete thought, and when two independent clauses are conjoined, you need to use a coordinating conjunction to create a compound sentence.

“Or” is a coordinating conjunction, and a comma should be placed before it when it is used to join two complete sentences.

For example:

  • Sarah will have to settle for the grade she received, or she will have to contact the dean and discuss the reasons why she deserves a better grade.
  • Pick the theater you want to go to this evening, or we will end up staying home to watch television instead.

Using “Or” in Lists

When creating a standard list of items in a series, you need to separate each item with a comma. The final comma or serial comma (also known as an Oxford comma) separates the second to the last item in the list from the final item. You also should include “and,” “or,” or “nor” preceding the final item.

For example:

  • You either need to make sandwiches, pack snacks and drinks, or figure out where to stop for groceries before we leave.
  • We still need to decide whether to complete the work in advance, work through the trip, or ask for an extension.

Although the much-debated Oxford comma technically does not need to be used, it does help clarify and separate list items to avoid any confusion. 

Using “Or” With an Appositive

An appositive is a noun or pronoun that is placed alongside another noun or pronoun to help describe it in another way. Appositives are offset in a sentence via a pair of commas using “or” since it is a common way to introduce another name or translation.

For example:

  • Introduction to High School, or Freshman 101, was a course dedicated to the organization.
  • Comment ça va, or how are you, is a common greeting in France.

Using “Or” to Introduce a Nonessential Clause

Inessential clauses are offset in a sentence to provide more detail or explanation. However, if the clause is removed, the sentence is still understandable to the reader. “Or” is not often used to introduce a nonessential clause, but on rare occasions, you can make it work.

For example:

  • Jonathan didn’t understand his homework, or he didn’t care, and rushed through it just to get it done.

Using a Comma After “Or”

You very rarely will place a comma after “or.” The only time this situation may occur is when “or” precedes a parenthetical phrase, and the author wants to emphasize the use of “or” to make it stand out. Parenthetical phrases are offset with a set of commas and are considered nonessential clauses.

For example:

  • You could either save your money or, if it were up to me, pay off your bill and start fresh.

Let’s Review

There are many instances in which you should place a comma before “or,” such as when you use it as a coordinating conjunction, in lists, or with appositives and nonessential clauses. On rare occasions, you can also place a comma after “or” when you emphasize its use preceding a parenthetical phrase.

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