Commas in a Series

Newsroom101

Commas between Elements in a Series
Use commas to separate elements in a series.

What is a series?

A series is several items separated by commas and a conjunction:

Red, white and blue
Pick up the laundry, buy toothpaste, get gasoline, return library book and cash check

In a simple series, omit the "serial" comma -- the last one before the conjunction:

Red, white [no comma] and blue
Pick up the laundry, buy toothpaste, get gasoline, return library book [no comma] and cash check

Note: Omitting the serial comma is one of the hallmarks of AP style. Some other stylebooks (such as APA) use this "extra" comma.
Note: Misusing this comma is one of the 20 most common grammatical errors.

Exceptions. There are times you need to use the serial comma (the comma before the conjunction).

When to use the "serial" comma:

If (at least) one element in the series uses a conjunction

He had coffee, a croissant, and ham and eggs.

In a "complex" series -- one where each item in the list is itself a complicated expression, and you need commas to keep the thought straight:

She could be late for many reasons -- because it is snowing, because her car would not start, because she could not find someone to take care of her dog, or for almost any reason.

Semicolons in a list. Sometimes you need to use semicolons instead of commas to clarify a list.

This normally happens:

When items in the list are long.
When items in the list contain commas of their own.

In those cases, separate the series with semicolons:

Elected to the council were Mark Roberts, 19, a sophomore from Miami, Fla.; Suzanne Idley, 20, a junior from Nashville, Tenn.; and Alberto Greenberg, 21, a senior from Hartford, Conn. [Esp. note the semicolon before the "and."]

Practice using commas and semicolons in a series.