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Comma Corner

Written by tutor Elizabeth B.

Commas are used to divide items on lists and to separate clauses in complex sentences from each other so that readers can follow the ideas more easily. The seven comma rules are not difficult, and they are explained here, with examples.

1. When a sentence has two clauses that could each be a sentence on their own, use a comma plus a coordinating conjunction such as and, if, but, or, nor, and because. When you are deciding whether to use the comma/conjunction combination, make sure that each clause contains a noun and a verb.*

Examples:  1. Wendy flew around Neverland, and Peter went looking for pirates.
                 2. Michael and Jane advertised for a perfect nanny, but they never imagined that she would float into London
                 on an umbrella!

*In each of these sentences, the second clause could be a sentence by itself, so you must use a comma before the conjunction.

“Peter went looking for pirates.”

“They never imagined that she would float into London on an umbrella!”

Comma Don’t: Never put a comma after a conjunction.

2. When the second clause cannot be a sentence on its own, do not use a comma.*

Examples:  1. Harry Potter and Ron Weasley are great friends and face many dangers together.
                 2. Many fans of the Harry Potter series have read all the books several times and will watch the movies over
                 and over.

*In these examples, the second clause in each sentence (“and face many dangers together” and “will watch the movies over and over”) is not a sentence on its own. Therefore, do not use a comma.

3. When using a comma to separate items in a list of three or more items, use a comma after each item and insert the word “and” between the second-to-last and last items. The use of a comma before “and” is optional, but I generally advise using it because it prevents the reader from thinking that the last two items on the list are a pair.

Examples:  1. Julie’s homework tonight consists of math, social studies, and English.
                 2. Max likes video games, comic books, anime, and science fiction.

4. Use a comma to divide two adjectives that appear directly before a noun.*

Examples:  1. Joey loved the colorful, imaginative paintings he made in art class.
                 2. Amelia’s disorganized, overcrowded room made it difficult for her to find the book she was reading.

Do NOT use a comma between two adjectives if one of them is a color, a size, or an age. Notice that “age” includes words such as new, old, and young. In these cases, the second adjective counts as part of the noun instead of as an adjective.

Examples:  1. The big red balloon floated away above the trees.
                 2. The angry old man yelled at the children for running in his garden.
                 3. The happy three-year-old ran around the house with her new puppy.

5. Use a comma to separate an introductory phrase from the main clause of a sentence. Introductory phrases can be single words or short phrases such as well, therefore, in contrast, on the other hand, yesterday, last week, next, afterwards, or any other “starter words.”

Examples:  1. Yesterday, I went to Amit’s birthday party.
                 2. In contrast, people who never exercise have less energy.

6. Use a comma to separate longer introductory phrases from the main clause of a sentence.

Examples:  1. Although I meant to clean my room, I was distracted by my favorite television show.
                 2. During the storm, we played games and made hot chocolate.

7. Commas are also used to identify modifying clauses that occur in the middle of a sentence. They are also called “appositive clauses.” You can identify an appositive clause because a) it lacks a noun or a verb; b) it can be removed from the sentence without changing the sentence’s basic meaning; or c) shows contrast.

In the examples below, try removing the appositive clauses. You will see that the main idea of the sentence remains the same. Appositive clauses add interesting details, but are not essential to the meaning of the sentence.

Examples:  1. We went to class, which was interesting, and then went out for pizza.
                 2. My uncle, who lives in Cleveland, is getting married.
                 3. Sasha enjoys warm winters, despite knowing they are caused by global climate change, because they
                 mean he can still ride his bike all over town.