Writing Skills

Use a comma to separate introductory words, phrases, or clauses. 

A comma is used to separate introductory words (besides, however, furthermore, therefore) and introductory phrases and clauses.

• Besides, I should know better.

A comma is used to separate introductory participial phrases, adverbial clauses, and prepositional clauses.

• Knowing I had more work to do, I stopped checking my phone.

An appositive is a word that follows a noun and explains it.

• Emily, a librarian, is well versed in information literacy skills.

Parenthetical expressions also explain or clarify the sentence. Some of the more common expressions are of course, I believe, after all, by the way, in my opinion, for example, to tell the truth.

• It was Jeremy, I believe, that made the first call.

Such words as however, moreover, nevertheless, otherwise, or therefore often appear parenthetically.

• I realized, however, that the mistake was my own.

Non-defining clauses provide additional information about the noun they modify. These clauses are typically separated by commas.

• Roger, who is my annoying roommate, always eats all of the pizza bagels.

When listing items (either words, phrases, or clauses) in a series, use commas to separate them. There are different views on whether a comma is needed before and. Some grammarians have stated that it is not needed, and some have said that adding a comma before and prevents confusion in a sentence. Whichever rule you decide to go by, make sure you are consistent throughout your writing whenever there are series of items joined by and.

• CORRECT: The presentation was made by Michael, David, and Carolina.
• CORRECT: The presentation was made by Michael, David and Carolina.

When joining two complete sentences, use a comma before a coordinating conjunction (and, or, for, nor, so, but, or yet).

• My name is Will, and I like solving mysteries.

With place names

• Austin, Texas is the capital of the state.

With the date

• June 16, 1955

When only month and date are given, no comma is necessary.

• Our next meeting is on June 18.

When two adjectives separately modify the same noun and can be inverted and connected with and, use a comma between them.

• The meal was full of complex, rich flavors.

Before quotations
He said, “I’m your best friend.”