Even experienced writers struggle with commas. While creative writing allows some flexibility for stylistic choices, business, academic, and technical writing depend on precise comma usage for clarity. If you follow a particular style guide for work or school, it’s worth reviewing the rules — some may surprise you. At Word Smarts, we use the Associated Press Stylebook (AP style), which reflects standard American English grammar, with some exceptions, notably using the Oxford comma. Here’s what AP style has to say about five tricky comma scenarios.
Learning how to tell time and read a calendar are skills learned as young children, but the rules for writing out dates can get confusing. The most basic AP-style format for a complete date is “Jan. 1, 2026.” In this style, the comma follows the numerical date to offset the year. On Word Smarts, however, we always spell out the months. Things get trickier when more details are added.
For instance, when Jan. 1, 2026, appears in the middle of a sentence, a second comma is needed to offset the date fully. (Note that in AP style, months except for May are abbreviated when used in full dates or with just the day.) Consider another example: “Feb. 12, 1809, marks the birthdays of both Abraham Lincoln and Charles Darwin.”
Moreover, adding a weekday to the date is treated as extra information (or “nonessential”) and should be set off with a comma: “Super Bowl LX takes place on Sunday, Feb. 8, 2026, in the San Francisco Bay Area.”
However, commas are not always required in dates. For instance, if you mention only the month and year of a date, commas are not needed: “April 1926 includes two famous birthdays: Pulitzer Prize-winning novelist Harper Lee and Queen Elizabeth II.” (Note that the month is not abbreviated when it appears alone or with just the year.) You can also omit the comma if you have a month and day with no year: “The gala takes place every year on June 6 in New York City.”
There are plenty of rules about adjective order, but just as important is knowing when to separate adjectives with a comma. Coordinate adjectives require a comma because they’re equal or interchangeable. Think “a hot, humid day” or “an old, tattered book.”
This rule still applies when more than two coordinate adjectives are listed, though you’re less likely to come across it: “A dark, dreary, dingy basement.” Consider this helpful test to determine if adjectives are coordinate: If “and” can be used between them, a comma is required.
When adjectives aren’t interchangeable, they’re considered “cumulative,” and they do not require a comma. These adjectives rely on a specific order to build on one another. For example, “a new moisturizing cream” and “old green rubber boots” are cumulative and don’t need commas. Remember the test from earlier: Placing “and” between these adjectives would sound awkward. This is your cue that adjectives are cumulative, and commas can be omitted.
An appositive is a noun or pronoun that explains or identifies another noun or pronoun. If the appositive provides essential information, commas aren’t needed. However, if the appositive is nonessential, commas are required to set off the extra information.
Consider the statement, “The Beatles singer John Lennon was expelled from college.” Here, the appositive “John Lennon” clarifies the noun “Beatles singer,” since multiple Beatles were singers. In this situation, commas are not used around his name because it is vital information. Writing, “The Beatles singer, John Lennon, was expelled from college,” would be incorrect; if you removed the words offset by commas, the sentence would be unclear.
Compare that to this example: “John Lennon, writer of the song ‘Imagine,’ was expelled from college.” Here, the appositive “writer of the song ‘Imagine'” is nonessential, adding detail without altering the meaning of the sentence. Because it isn’t vital to the goal of the statement, and the meaning doesn’t change if it’s removed, commas are needed to set it off.
This rule gets trickier when prior knowledge of the reader is required. For instance, imagine you have two sisters. If you write, “My sister Alice sent a birthday card,” the appositive (“Alice”) does not require commas because her name is essential to the sentence’s purpose — you must know which sister sent it. But if Alice were your only sister, you would write, “My sister, Alice, sent a birthday card,” since her name is no longer necessary for identification. Due to the complexity of some scenarios, this rule is often overlooked.
Sometimes commas are overused in introductory phrases. Some writers have a knee-jerk reaction to introductions, automatically adding a comma to set off an introduction no matter the length or context. However, AP style allows you to omit the comma if the introductory phrase is short and unambiguous.
For instance, “Soon it will begin” doesn’t require a comma because “soon” is just one introductory word and there is no ambiguity. The same goes for “By evening we were tired” or “On Saturday we went home.” These are cases where including a comma is optional and a matter of preference.
Long introductory phrases, however, should always be followed by a comma: “While primarily celebrated in the United States, Groundhog Day is a holiday that stems from European folklore.” Here, the comma helps separate the setup from the main idea. When constructing longer introductory phrases, keep an eye out for dangling modifiers.
When directly addressing someone, a comma must set off the name, no matter where it appears in the sentence. For example, all three of these sentences feature correct comma placement: “You’re funny, Fred.” “Fred, you’re funny.” “You, Fred, are funny.”
This rule is often overlooked in everyday emails and texts, such as “Thanks, Jack!” or “I’m sorry, Jill.”
But the rules of direct address become even less obvious when a common noun replaces a name. For example, “I’m going to be late for practice today, coach,” requires a comma because “coach” is being addressed directly. The same goes for “Thanks, professor, I appreciate the extension,” which requires two commas sandwiching “professor.”
In these cases, commas do more than follow a rule — they prevent confusion or misunderstandings. Just consider the difference between the correct phrase “Let’s eat, Grandpa!” and the much more alarming “Let’s eat Grandpa!”
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