Commas

Between Items in a list

If you have a list of three or more items or phrases, use a comma to separate each one.

I bought some new shoes, a backpack, some notebooks, and a hoodie.

Between two independent clauses

A comma plus a conjunction (for, and, nor, but, or, yet, so) join two independent clauses together in one sentence.

I grew up in Ogden, but my school of choice is the University of Utah.

Before & After descriptive phrases

A descriptive phrase is a short phrase that adds description to the sentence as a whole or to a particular noun. Phrases do not have a subject and verb together. Commas are used before and after the descriptive phrase.

Note: Do not confuse a phrase with a subordinate clause, which has a subject and verb.

Jane Austen, my favorite author, wrote Pride and Prejudice.

"my" being the noun and "favorite author" being the descriptive phrase

Before & After a verbal phrase

A verbal phrase looks like a verb but acts as a modifier or noun.

Walking out of the grocery store, Mark realized he forgot to buy eggs.

"Walking out" being the verbal phrase describing when Mark had his realization

After a subordinate clause

A subordinate clause has [a subordinate conjunction + subject + verb] and always attaches to an independent clause. If the subordinate clause comes first in the sentence, a comma must come after it.

When I need to do homework, I always find myself procrastinating.

"I need to do homework" is the subordinate clause and "find myself" the independent clause

I always find myself procrastinating when I need to do homework.

"myself procrastinating" is the independent clause and "need to do homework" the subordinate clause

Common Subordinate Conjunctions: after, although, as, as if, because, before, even though, if, in order that, rather than, since, so that, than, that, though, unless, until, when, where, whether, while.

Before & after non-essential elements

Clauses that begin with "which," "who," and "where” usually add extra information about a noun in a sentence. These clauses are considered non-essential if the information in the clause does not make the noun go from vague to more specific.

Do not use commas with clauses that begin in "which," "who," or "where" if the information is essential in making the noun more specific.

Note: Never use commas with clauses that begin with “that."

Mr. White, who was my English 101 professor, is still teaching.
(The fact that he was your English 101 professor is nonessential.)

That man who is wearing the yellow shirt was my English 101 professor.
(The yellow shirt is essential to distinguish which man you are talking about.)

With "Such As"

"Such as" and "including" only need a comma before them if they come at the end of the sentence. If "such as" is in the middle of the sentence, it may not need a comma at all.

I enjoy books that critique social norms, such as Pride and Prejudice.
I enjoy books such as Pride and Prejudice that critique social norms.