When To Use A Comma: Rules And Examples

It’s hard to imagine a world without punctuation marks, but the ancient Greeks themselves struggled to read and write sentences (if you can call them that) without the navigational aid of spaces, punctuation marks, or uppercase and lowercase letters. (itwouldlooksomethinglikethis)

So yes, while we may complain about learning the rules of grammar, we should all admit reading is much easier with a guide like a comma to show the way. The least we can do is learn how to use it properly!

What is a comma (,)?

A comma (,) signifies a short pause in a sentence. It can also divide clauses (“parts of a sentence”) or items in a list. And, it is often used to create division or to improve the clarity of a sentence. Clearly, a comma has many roles as a punctuation mark. Here are some more specifics.

The comma vs. the semicolon

First things first, a comma can be easily confused with a semicolon (;). But as the examples and rules here will clarify, a semicolon is used to indicate a more significant break than a comma (but less significant than a period). Often, reading a sentence aloud can help you decide which punctuation mark is more appropriate.

The comma vs. the colon

The difference between a comma and a colon (:) is even more pronounced. For example, a colon can be used to introduce a list—but you’ll still need commas to separate the items in the list. For example, Here’s a list of groceries I need: a loaf of bread, a quart of milk, and a stick of butter.

When to use a comma

To signal a pause

In writing, commas usually signal a pause that would be heard if the sentence were read aloud. It’s a short, soft pause, as opposed to the longer pause signified by a period.

To separate adjectives

Commas separate adjectives when the order of the adjectives doesn’t affect the meaning. For example: She gave him a soft, comfortable blanket. The order of the adjectives soft and comfortable could be reversed, so they’re separated by a comma.

However, in “delicious chocolate cake,” the word chocolate is a direct modifier of cake. So, the order of delicious and chocolate shouldn’t be flipped. (In this case, the comma isn’t needed.)

To separate items in a list

Commas also separate items in a list, and this is another use of a comma that quickly comes to mind. A list can be simple, as in a series of words: He bought milk, eggs, and bread at the store. Commas also separate lists of longer phrases: The dog ran out the front door, through the mud, and dashed out the open gate.

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When using quotes

When writing a conversation between two people using quotes, commas help a reader keep track of who is speaking. A comma is used to separate the name of the person speaking (or a pronoun) and a verb. For example:

  • “I’m not feeling well today,” she said.
  • “I’m not feeling well today,” Stella confessed, “because I stayed up too late last night.”

To separate nonrestrictive (nonessential) clauses

A comma can also separate nonessential words from the essential parts of a sentence. For example, Patty came to visit doesn’t need a comma. But, Patty, my second cousin, came to visit, does need commas to set apart the nonrestrictive clause (the part of the sentence that isn’t necessary for the sentence to be understandable): my second cousin.

Overall, these nonrestrictive clauses basically just add extra information to a sentence.

When you use as well as in a nonrestrictive clause, the same rules apply: Deborah, as well as her assistant, decided to attend the convention.

However, when there is a restrictive clause (a part of the sentence that adds essential information), you shouldn’t offset it with commas, even when it contains as well as. An example is: The employee discount policy applies to full-time workers as well as contractors. If you remove as well as contractors, the sentence loses some essential information.

To connect two independent clauses

Commas are also used to separate independent clauses (phrases that can stand on their own) when a conjunction (like and) is used, as in the compound sentence: Mark went to the store, and he bought eggs.

To set off an introductory phrase

Commas set off introductory participial phrases as in: Reading over her notes, Julie realized she missed an important detail.

To write numbers with more than four digits

You can also use commas to divide sets of numbers. For example, in numbers over 1,000 the comma separates sets of three digits at a time. For example, in 1,000,000 there are two commas (one for every three decimal places).

To write dates and addresses

In a street address, commas divide each piece of information. For example, the address of the Metropolitan Museum of Art in New York is 1000 Fifth Avenue, New York, New York 10038.

What about greeting cards? Learn about the right way to start and sign off that birthday card to grandma!