Serial Comma | Rules, Examples & Definition

The serial comma (aka Oxford comma or Harvard comma) is a term that describes the use of a comma before the conjunction in a list of three or more items (e.g., the comma before “and” in “pancakes, scrambled eggs, and bacon”). The name comes from the fact that it’s used in a series (list).

The serial comma is optional—it’s not an error to leave it out or to include it. Different style guides and publishers have different recommendations, but academic style guides normally recommend using it.

If you need to follow a particular style, check out our quick summary of who recommends the serial comma below. If you don’t, the choice is up to you. Just write according to your own preference.

Serial comma examples

The serial comma can be used (or left out) in any list of three or more items. It can be used regardless of what those items are (e.g., nouns, verbs, adjectives, longer phrases) and whether the conjunction used is “or” or “and.”

Examples: Oxford comma
The concert tickets included backstage passes, VIP seating, and a meet-and-greet with the band.

Springsteen played his greatest hits, including “Born to Run,” “Dancing in the Dark,” and “Thunder Road.”

Do you prefer your tea black, with milk, with sugar, or with both milk and sugar?

I’ve never climbed a mountain, skydived, or run a marathon.

Note that the other commas in the list are not optional. You always need commas between the earlier items in the list, whether or not you add the serial comma:

  • The recipe calls for flour eggs milk and sugar.
  • The recipe calls for flour, eggs, milk and sugar.
  • The recipe calls for flour, eggs, milk, and sugar.

But you should use no commas in a list of only two items. Adding one is grammatically incorrect:

  • My favorite colors are red, and blue.
  • My favorite colors are red and blue.

Arguments for and against the serial comma

Various arguments are used for and against the serial comma. The main ones are summarized in the table below.

  • Pros
  • Cons
It makes lists clearer in some cases. It makes lists less clear in some cases.
All other list items are separated by commas, so it’s more consistent to add a comma before the final one as well. It takes up space on the page—mainly relevant in contexts like newspapers, where space is limited.
It resembles speech more closely (people tend to pause before saying the last item in a list). Most people instinctively leave it out in writing; adding it can make your text look overly stiff and formal.

The argument about clarity is the main point of debate. The following section examines it in more detail.

Does the serial comma make lists clearer?

Advocates of the serial comma claim that it clears up confusion in two kinds of lists:

Lists where items could be misread as appositives

Look at the ambiguous list below:

  • I met the authors, Maya Singh and Harper Martin.

It’s not clear whether this is a list of three items (“the authors,” “Maya Singh,” and “Harper Martin”) or whether “Maya Singh and Harper Martin” is an appositive—a phrase that identifies “the authors.”

Adding the serial comma makes it completely clear that Maya Singh and Harper Martin are not the same people as the authors:

  • I met the authors, Maya Singh, and Harper Martin.

But it’s just as easy to find examples where adding the serial comma actually makes the list less clear. For example, when the first item is singular instead of plural:

  • I met the author, Maya Singh, and Harper Martin.

Is Maya Singh the author, or are they two different people? Here, leaving the comma out actually removes the ambiguity. “Maya Singh” can be read as an appositive only if it’s surrounded by commas:

  • I met the author, Maya Singh and Harper Martin.

Neither using the comma nor omitting it fixes these problems in all cases, so it can’t be counted as a point for or against the serial comma. The ambiguity is more reliably resolved by changing the order of the list items or rephrasing:

  • I met Maya Singh, Harper Martin, and the author.
  • I met the authors, as well as to Maya Singh and Harper Martin.

Lists where individual items contain conjunctions

Consider the list below:

  • The flavors available include roast beef and mustard, salt and vinegar and sweet chili.

The intended meaning is that “salt and vinegar” is one flavor, “sweet chili” another. But it’s possible to instead interpret “salt” as one flavor and “vinegar and sweet chili” as another.

Adding the serial comma clarifes which words belong together to describe each flavor:

  • The flavors available include roast beef and mustard, salt and vinegar, and sweet chili.

Unlike with the appositives issue, there are no cases where adding the comma causes confusion. This is a clear point in favor of the serial comma.

Using the serial comma flexibly

A third stance is that you shouldn’t always add or always omit the serial comma but rather be flexible: decided on a case-by-case basis, adding it when it helps to resolve ambiguity and otherwise omitting it.

This has some clear advantages. There are cases where the extra comma improves clarity and cases where it creates problems, so flexibility is helpful.

But it also has some potential disadvantages. If you follow one style or the other consistently, an attentive reader will notice any exceptions and understand that they’re deliberate. But if you mix the two styles, your text may simply look inconsistent.

Who recommends the serial comma?

Different style guides, publishers, and language authorities have different recommendations about the serial comma. Some require it, some advise against it, and some suggest being flexible.

Most major academic style guides do recommend the serial comma. Journalistic style guides are less likely to be in favor, since the extra comma takes up space. And the serial comma is generally less common in UK English than US English.

Here on the Scribbr Knowledge Base, we aim to use the serial comma consistently in our articles. But in our Proofreading & Editing service, we follow the customer’s lead, unless they indicate that they’re following APA Style.

The table shows the recommendations of various prominent language authorities.

Who recommends the serial comma?
  • For
  • Against (or flexible)
AMA (American Medical Association): “Use a comma before the conjunction that precedes the last term in a series.” AP (Associated Press): “Use commas to separate elements in a series, but do not put a comma before the conjunction in a simple series.”
APA (American Psychological Association): “Use a comma between elements (including before and and or) in a series of three or more items.” Cambridge University Press: “In British practice there’s an Oxford/Cambridge divide [with Oxford in favor and Cambridge against].”
Chicago/Turabian: “Always use a comma before the conjunction that introduces the last item [in a list].” The Economist: “Some style guides require [the serial comma]; others (including The Economist’s) do not.”
IEEE (Institute of Electrical and Electronics Engineers): “In a series of three or more terms, use a comma immediately before the coordinating conjunction.” The Guardian: “Straightforward [lists] … do not need [a serial comma], but sometimes it can help the reader.”
MHRA (Modern Humanities Research Association): “In an enumeration of three or more items, … insert commas after all but the last item, to give equal weight to each enumerated element.” New York Times: “In general, do not use a comma before and or or in a series.”
MLA (Modern Language Association): “Use commas to separate words, phrases, and clauses in a series. The final comma in a series is known as the serial (or Oxford) comma.” The Times: “Avoid the so-called Oxford comma.”
Oxford University Press: “Given that the final comma is sometimes necessary to prevent ambiguity, it is logical to impose it uniformly.”

Using semicolons instead of commas

Another way to punctuate complex lists (lists where individual items include conjunctions or commas) is to use semicolons instead of commas between the items. When semicolons are used, there is always a semicolon before the final item. Omitting it is an error.

This approach is best when a list might otherwise be hard to read.

Example: Complex list with commas
For dinner, we had grilled chicken with a side of quinoa salad, made with red quinoa, cucumber, feta cheese, and a homemade dressing of olive oil, lemon juice, and Dijon mustard, roasted asparagus drizzled with balsamic glaze, and garlic bread made with freshly minced garlic, salted butter, and French baguette.

The list above is grammatically correct but quite difficult to parse. Individual items in the list contain commas, conjunctions, and lists of their own. On first reading, it’s difficult to understand which ingredients are part of which dish. Using semicolons makes it easier.

Example: Complex list with semicolons
For dinner, we had grilled chicken with a side of quinoa salad, made with red quinoa, cucumber, feta cheese, and a homemade dressing of olive oil, lemon juice, and Dijon mustard; roasted asparagus drizzled with balsamic glaze; and garlic bread made with freshly minced garlic, salted butter, and French baguette.

Here, the lists within the list still use commas, but the larger list is divided using semicolons. This makes the sentence much simpler to parse.

Exception: No serial comma before an ampersand (&)

In one case, even style guides that normally recommend the serial comma tend to say that it shouldn’t be used. This is when the ampersand symbol (&) is used instead of the word “and.” The normal approach in this case is to leave the comma out:

  • Definition, Examples, & Synonyms
  • Definition, Examples & Synonyms

Note that in academic writing, you should normally spell out “and” in full anyway. Using an ampersand instead in the main text is considered overly informal. So this issue won’t come up very often.

But some citation styles do require the use of ampersands to save space between author names in in-text citations or reference lists. One of these, APA, requires the serial comma even when the ampersand is used, so bear in mind that this rule is not universal.

Example: APA Style citation with serial comma before ampersand
Jones, F., Sanders, N., & Merkus, J. (2023). The citation manual for students: A comprehensive guide (4th ed.). Wiley.

Other interesting language articles

If you want to know more about commonly confused words, definitions, common mistakes, and differences between US and UK spellings, make sure to check out some of our other language articles with explanations, examples, and quizzes.

Frequently asked questions

What is a serial comma?

The serial comma is a comma that comes before the final item in a list of three or more items. It comes before the conjunction (“and” or “or”): “John, Mandy, and Lupita.” Without the serial comma, the same phrase would be “John, Mandy and Lupita.”

The serial comma is optional; different style guides have different recommendations. But most academic style guides do recommend using it consistently.

The serial comma is also called the Oxford comma or the Harvard comma.

What’s the difference between the serial comma and the Oxford comma?

There’s no difference between the serial comma and the Oxford comma. They’re two different names for the same thing: a comma before the conjunction (“and” or “or”) in a list of three or more items (e.g., “ham, cheese, and tomato”).

The Oxford comma or serial comma is optional but recommended by most academic style guides. It’s sometimes also called the Harvard comma.

Do you put a comma before “and” in a list?

The comma before “and” (or comma before “or”) at the end of a list is optional. It’s referred to as an Oxford comma or serial comma. Most academic style guides recommend adding it (“salt, pepper, and paprika”). But it’s also not a grammatical error to write a list without it (“salt, pepper and paprika”). Some authorities, such as the AP Stylebook, do recommend leaving out the comma.

The Oxford comma tends to improve the clarity of lists, especially complex lists, by showing clearly where one list item ends and another begins. In academic writing, it’s recommended to use it.

Is the Oxford comma necessary?

The Oxford comma (a comma placed before the final item in a list of three or more items) is optional. It is not an error to leave it out. “Salt, pepper, and vinegar” and “salt, pepper and vinegar” are both grammatically correct.

Different style guides have different recommendations about using it. Most academic style guides (e.g., APA, MLA, Chicago) recommend using the Oxford comma consistently, so this is typically the best approach in academic writing.

Note that the earlier commas in a list are not optional: “salt pepper and vinegar” is not grammatically correct.

Do I need to use the serial (Oxford) comma in APA Style?

Yes, APA language guidelines state that you should always use the serial comma (aka Oxford comma) in your writing.

This means including a comma before the word “and” at the end of a list of three or more items: “spelling, grammar, and punctuation.” Doing this consistently tends to make your lists less ambiguous.

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Jack Caulfield

Jack is a Brit based in Amsterdam, with an MA in comparative literature. He writes for Scribbr about his specialist topics: grammar, linguistics, citations, and plagiarism. In his spare time, he reads a lot of books.