The Oxford comma—also called the serial comma—is the comma placed before the final and or or in a list of three or more items.
Basic examples
With the Oxford comma:
- We bought apples, oranges, and bananas.
- She invited her parents, her manager, and her neighbor.
- The flag is red, white, and blue.
- You can pay by cash, credit card, or check.
Without the Oxford comma:
- We bought apples, oranges and bananas.
- She invited her parents, her manager and her neighbor.
- The flag is red, white and blue.
- You can pay by cash, credit card or check.
Both versions may be grammatically acceptable, depending on the style guide being followed. The key is consistency.
Examples where it improves clarity
The Oxford comma can prevent the final two items from appearing to form a single unit.
Potentially confusing:
The conference included the directors, a teacher and a scientist.
This might mean the conference included:
- the directors,
- a teacher,
- a scientist;
or it could suggest that the directors themselves are “a teacher and a scientist.”
Clearer:
The conference included the directors, a teacher, and a scientist.
Another example:
Without an Oxford comma:
I dedicate this book to my parents, a famous actor and a renowned scientist.
This humorously suggests that the writer’s parents are the actor and scientist.
With an Oxford comma:
I dedicate this book to my parents, a famous actor, and a renowned scientist.
Now the sentence clearly refers to four people or groups: two parents, one actor, and one scientist.
Examples in different contexts
Everyday writing
- For breakfast, I had eggs, toast, and coffee.
- Remember to bring sunscreen, water, and a hat.
- The job requires patience, accuracy, and good communication.
Business writing
- The report covers revenue, operating costs, and projected growth.
- Please send the invoice, signed agreement, and payment details.
- Our priorities are customer retention, product quality, and employee development.
Academic writing
- The study measured speed, accuracy, and comprehension.
- Participants were grouped by age, education, and income.
- The theory has historical, political, and cultural implications.
More complex list items
The Oxford comma is especially useful when list items contain their own conjunctions:
The program includes research and development, sales and marketing, and customer support.
It also helps with longer phrases:
Applicants must submit a completed form, a copy of their identification, and a letter explaining their qualifications.
When to use it
Use the Oxford comma when:
- Your required style guide calls for it.
- Omitting it could cause confusion.
- You want consistent punctuation across lists.
Many book publishers and academic style guides favor it. Some newspaper styles commonly omit it unless clarity requires it. Even if your usual style excludes the Oxford comma, adding one is often wise when it prevents ambiguity.
A simple rule to remember is:
First item, second item, and third item.