Even though commas are one of the most widely used punctuation marks, many people are confused about common usage. Both students and seasoned writers can have a hard time deciding when to use a comma.
The easy answer to the question of how to use a comma is to use when there is a brief pause. The reality of comma usage is far more complex because this form of punctuation has many different uses. To make things even more confusing, there are few definite rules to comma use. Most of the hard and fast rules we were taught back in English class are actually guidelines that are often be ignored.
The Basic Rules of Comma Usage
When you are using two interchangeable adjectives to describe a noun
Example 1: It was a shiny, fast car.
Example 2: It was a very expensive luxury hotel.
No comma is used here because expensive and luxury are not interchangeable.
When you need to separate words or groups of words in a list
Example 1: The menu consisted of burgers, fries, hot dogs, and onion rings.
The comma before "and" is called the "Oxford comma", and it is considered optional. Some of the stylebooks used by journalists and professional writers recommend dropping it. There are some times when the Oxford comma is necessary; for example, when the word "and" appears in a list.
Example 2: The dessert options consisted of pie, coffee and cake, cheese, fruit and ice cream.
When an independent clause is added to a sentence by a connecting word such as and
Example 1: She started the car, and she drove away at a high speed.
The comma can be eliminated in a very short sentence.
Example 2: I cook and he eats.
To avoid the creation of common grammatical errors such as run-on sentences and comma splices
Example 1: After he ate the pot roast for dinner, he washed the dishes.
Example 2: She washed the car, and she changed the oil.
When you need to set off an expression that interrupts the flow of a sentence
Example 1: Not surprisingly, he was extremely nervous about the upcoming exam.
Example 2: As a rule, she was always afraid to drive after dark.
When you use certain words, such as yes, no, why, or hello, to introduce a sentence
Example 1: No, you cannot have any cake until after you finish your Brussels sprouts.
Example 2: Hello, my name is Maynard Noodlehead.
When you need to set off a title, name, nickname, or term of endearment from a person who is being directly addressed
Example 1: Top of the morning to you, sergeant.
Example 2: Yes, Virginia, there is a Santa Claus.
When you need to separate the name of a community from the name of a geographic region such as a state, province, or nation
Example 1: I mailed the letter to Pueblo, Colorado, yesterday.
Example 2: She traveled to Birmingham, England, to visit her mother.
When a title such as Jr. or Sr. is added after a person’s name. A comma is usually placed after the preceding word in mid-sentence, but this rule is not considered mandatory
Example 1: Franklin Jones, Sr., has been hired as the new college president.
Example 2: He hired Adolph Smith, Jr., as the new cashier.
When you need to separate a day of the month from a year in a date
Example 1: She was born on May 18, 1968, in Kingston, Ohio.
Example 2: The July 2013 issue of the magazine did not contain a photo essay.
A comma is not necessary when the specific day is not mentioned.
When a title or degree is mentioned after a person’s name
Example 1: Jane Jones, PhD, was named professor of history at the university.
Example 2: The will named Albert Cosby, attorney at law, as the executor of the estate.
When non-essential information is inserted into a sentence
Example 1: Joseph, who is a former basketball player, lives next door to me.
Example 2: Her favorite novel, The Grapes of Wrath, was the subject of the lecture.
When a nonessential clause, word, or phrase is added to a sentence
Example 1: The mailman, who is my brother-in-law, did not come today.
Example 2: There were just three items, onions, parsley, and broth, on her shopping list.
Nonessential words or phrases that appear midsentence are always enclosed by commas.
When a quotation comes at the beginning of a sentence even if it is just one word
Example 1: “Nuts,” the general replied to the enemy’s ultimatum.
Example 2: “I love you,” the man said to the woman.
When you need to introduce or interrupt a direct quotation
Example 1: He opened the proceedings by saying, “Welcome to the party.”
Example 2: “Hello, my name is Bill,” he said, “and I will be your guide.”
When two parts of a sentence contrast dramatically from each other
Example 1: The van belongs to the company, not to you.
Example 2: Leave the dog alone, he just wants to sleep.
When the term etc. is placed in a sentence
Example 1: I purchased franks, beans, ketchup, etc., when I was at the store.
Example 2: Her collection consisted of rubies, diamonds, sapphires, etc.
When you use an introductory word, phrase, or term such as for instance, e.g., or i.e. in a sentence
Example 1: You will be required to show proper identification, e.g., a driver’s license, to be granted admittance.
Example 2: He was hired to deal with certain problems, namely, the decline in sales and poor customer service.
Example 3: She is not a good cook; for example, she always burns the eggs.