Commas come before coordinating conjunctions (for, and, nor, but, or, yet, so) when they link two independent clauses*:
It was raining, and I was hurrying to get home.
She felt terrible, but she went to class anyway.
Commas separate items in a series, including coordinate adjectives:
He bought bananas, apples, oranges, and cheese.
She had long, dark, straight, thick hair.
Commas set off parenthetical elements such as an appositive, which is a noun phrase or clause that renames or describes the noun directly beside it, and nonrestrictive relative clauses:
The Washington monument, a massive obelisk, was completed in 1884.
My parents, who met each other in 1962, have been married for 50 years.
Commas set off transitional phrases:
On the other hand, many diets decrease stamina and strength.
As a matter of fact, American football was derived from rugby.
Many people, however, are allergic to cats.
Commas follow introductory clauses and phrases:
On the way home, I stopped to buy groceries.
Because it was raining, I took a taxi home.
To our surprise, they were brothers.
Use commas for direct address, tag questions, mild interjections, and yes/no:
I hate to say this, John, but this relationship just isn’t working out.
You like chocolate, don’t you?
Well, I might have time for lunch with you next week.
Yes, you must do the homework.
Commas indicate direct quoted speech: He said, “Let’s go,” and we did.
He said we should go, and we did.
Commas go inside quotation marks:
He had heard about “oleo,” but he didn’t know what it was.
- Semicolons connect two independent clauses that are closely related:
The book is informative; it has helpful charts and graphs.
My brother is going to Spain for the summer; he will be studying Spanish.
- Semicolons separate three or more items in a series that already have commas in them:
I like big, purple shirts; red, high-heeled shoes; and fluffy, yellow pillows.
I live with Larry, a student; Moe, an executive; and Curly, a cop.
- Semicolons separate two independent clauses that are joined by a transition word or phrase:
It is important to get enough sleep; however, too much sleep can be bad for your health.
Jack did not eat the leftovers in the fridge; instead, he ordered a pizza.
- Semicolons go outside quotation marks:
He had heard about “oleo”; he didn’t know what it was.