What punctuation is used to separate items in a series if the items themselves contain commas?

The colon ( : ) and semicolon ( ; ) are frequently used incorrectly in place of each other. The two punctuation marks serve very different purposes, and should not be used interchangeably.

Colon

A colon is used to give emphasis, present dialogue, introduce lists or text, and clarify composition titles.

Emphasis—Capitalize the first word after the colon only if it is a proper noun or the start of a complete sentence. (She had one love: Western Michigan University.)

Dialogue—Write the speaker's name, followed by a colon and his or her statement. (Reporter: What is the Western Edge? Dunn: It is a strategic plan for promoting student success.)

Introduce lists, text or tabular material—Capitalize the first word after the colon only if it is a proper noun or the start of a complete sentence. (Our future is dependent on three things: sustainability, diversity, and enhancing our strength and health.)

Clarify the titles of books, lectures and other compositions—Use a colon in titles that express two parallel ideas. The words on either side of the colon should be able to stand on their own. (He wrote "Crisis Management by Apology: Corporate Response to Allegations of Wrongdoing.")

Semicolon

A semicolon has two general uses: to clarify a series and to indicate two closely related sentences.

Series—If one or more elements in a series contain a comma, use semicolons to separate them. Include a semicolon before the final conjunction. (Members of the Western Jazz Quartet are Tom Knific, bassist; Trent Kynaston, saxophonist; Steve Zegree, pianist; and Tim Froncek, drummer.)

Two closely related sentences—For the most part, you should use a semicolon only where you could also use a period, but want to demonstrate a relationship between two complete sentences. (Good grades are integral to student success; a strong support network is also important.)

Perhaps no mark of punctuation ruffles feathers more than the serial comma (also called series comma, Oxford comma, and Harvard comma). This comma precedes the final item in a list or series, before the word and or or. With the exception of newspapers, most publications use the serial comma, because it helps writers avoid ambiguity. Who would object to unambiguous prose? you might ask. Fair-weather comma users: publications that do not require the serial comma may use it only when misreading results. Proponents of the serial comma, like the MLA, would decry the inconsistency of the use-it-when-you-need-it approach and advocate using the serial comma in all series of three or more items or phrases.

Here’s an example where omitting the serial comma results in ambiguity:

Without a serial comma placed after peach or after mango, it isn’t clear if “peach and mango” is one flavor or if “mango and pineapple” is.

Here’s another example:

As written, the sentence might mean that Deirdre is a friend of Sam’s and also his dentist. But, alternatively, the sentence might mean that Sam met three people, not one: Deirdre, a friend, and his dentist. Without the serial comma, there’s no way to know.

Serial Semicolons

When items in series themselves contain commas, additional punctuation is needed to clarify the items. Consider this sentence:

Here, commas aren’t enough to clarify the items in the series: is the councilwoman named Suzette Tanner or are Suzette Tanner and the councilwoman two people? Adding serial semicolons provides clarity:

The semicolons make it clear that there are four speakers. To use serial semicolons, place them wherever you would normally place serial commas, to separate like terms. Here’s a more complex example where serial semicolons are needed:

The addition of serial semicolons makes clear which items belong together and makes the sentence easier to read:

Still not convinced of the importance of the serial comma? A court ruling in a labor dispute earlier this year upped the stakes of this normally low-profile punctuation mark. The decision centered on the absence of a serial comma in a Maine state law, which could end up costing a company millions of dollars in overtime pay to truck drivers. An appeals court agreed with the drivers that the missing comma rendered the interpretation of the law ambiguous, and the lawyer representing the drivers credited the absence of the comma with winning them the case (Victor). A win for the drivers and for champions of the serial comma!

Work Cited

Victor, Daniel. “Lack of Oxford Comma Could Cost Maine Company Millions in Overtime Dispute.” The New York Times, 16 Mar. 2017, www.nytimes.com/2017/03/16/us/oxford-comma-lawsuit.html.

Punctuation within sentences can be tricky; however, if you know just a few of the following rules, you will be well on your way to becoming a polished writer and proofreader.

Rule: Use a comma between two long independent clauses when conjunctions such as and, or, but, for, nor connect them.
Example: I have painted the entire house, but she is still working on sanding the floors.

Rule: If the clauses are both short, you may omit the comma.
Example: I painted and he sanded.

Rule: If you have only one clause (one subject and verb pair), you won’t usually need a comma in front of the conjunction.
Example: I have painted the house but still need to sand the floors.
This sentence has two verbs but only one subject, so it has only one clause.

Rule: Use the semicolon if you have two independent clauses connected without a conjunction.
Example: I have painted the house; I still need to sand the floors.

Rule: Also use the semicolon when you already have commas within a sentence for smaller separations, and you need the semicolon to show bigger separations.
Example: We had a reunion with family from Salt Lake City, Utah; Los Angeles, California; and Albany, New York.

Rule: A colon is used to introduce a second sentence that clarifies the first sentence.
Example: We have set this restriction: do your homework before watching television.
Notice that the first word of the second sentence is not capitalized. Whether to capitalize the first word after a colon depends on the stylebook or style guidelines you are following. If you have multiple sentences following the sentence with the colon and you bullet or otherwise itemize them, capitalization and punctuation are optional. For example, if each bullet or numbered point is a complete sentence, you might capitalize the first word and end each sentence with proper ending punctuation. The rule of thumb is to be consistent.

Rule: Use a colon to introduce a list when no introductory words like namely, for instance, i.e., e.g. precede the list.
Example: I need four paint colors: blue, gray, green, and red.

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