Missing Comma

The comma is the most common form of punctuation within a sentence. Learning five basic rules about comma usage will help you punctuate your sentences correctly.

Make sure to use a comma to separate two main clauses in a sentence.

A compound sentence is two independent clauses (each with its own subject and verb that creates a complete thought) that are joined by a coordinating conjunction (and, but, or) and a comma. For example:

Juan's school has an excellent bilingual education program in Chinese, but it offers few Spanish classes.

Unless the sentence is very short, you should usually use a comma before the coordinating conjunction in a compound sentence. For example:

The rise of the Internet has made it easier to do research but much of the information on the Internet is unreliable.

This sentence should contain a comma after the word research and before the conjunction but.

Where should the comma be placed in the next sentence?

Choosing which universities I wanted to apply to was easy but deciding which one I want to attend next year is a more complicated decision.

The comma should be placed after the word easy and before the conjunction but.

Make sure to use a comma after introductory word groups.

After a short introductory group, for example, you do not need to use a comma.

On Tuesday I take karate lessons from a very disciplined instructor.

However, inserting the comma after an introductory word group will take care of many common mistakes in comma usage. For example:

After I take karate lessons on Tuesdays, I often go out to eat Chinese food with my father because it gives us a chance to spend time together.

Make sure to use a comma to separate items in a series.

When you write a list or a series of words, use a comma to separate each element. For example:

Tomorrow I have final exams in chemistry, English literature, and French.

Use a comma between coordinate adjectives when they each modify a noun separately.

Coordinate adjectives are two independent adjectives that modify the same noun. This means that each of these words could be used alone to modify the noun:

My history instructor is charismatic and irreverent.

Instead, you could compress the description by making the words "charismatic" and "irreverent" coordinate adjectives and by placing them both before the noun. This would allow you to say more about the day. For example:

My charismatic, irreverent history instructor is always making jokes about the administrative staff.

Not all adjectives, however, can be combined in this way. To test whether you can make adjectives coordinate, add the word "and" between the two adjectives. If you have not changed the meaning of what you want to say, you can make the adjectives coordinate. Generally adjectives that have to do with size, color, and number cannot be made coordinate and do not need to be separated by a comma. For example:

My three older sisters have given me a lot of valuable advice about getting along with girls.

Putting "and" between "three" and "older" sounds awkward. Therefore, these adjectives are not coordinate and do not require a comma between them.

Make sure to use commas to set off parenthetical information in a sentence.

Parenthetical information is considered additional information that is not necessary to the meaning of the sentence. When you are adding this kind of descriptive information, whether at the beginning, middle, or end of a sentence, separate it from the rest of the sentence by commas. For example:

Gabriel grew up along the coast, where marine life is still vibrant and common, and enrolled in college at the University of Texas.

Can you see that the words "where marine life is still vibrant and common" is additional information that is not necessary to the meaning of the rest of the sentence? Commas help to rank the importance of meaning in this sentence. For example:

Gabriel, who says he wishes he had grown up in a city, has chosen marine biology as his major.

Sometimes, the information in the sentence restricts or helps to make the meaning of the sentence clearer. In this case, you do not need to set off the information with commas. For example:

Gabriel likes exploring the beach where there are dozens of especially deep tide pools and extra large boulders that collect different shellfish.

Here, if you were to put a comma after beach, you would not be saying the same thing. Many beaches have tide pools. This beach has tide pools that are especially deep and have extra large boulders. Therefore, the additional information is restrictive and essential to the meaning of the sentence and should not be set off from the rest of the sentence with commas.

There are other uses for commas.

Use commas to set off the name of a city from a state:

Pendleton, Oregon
Los Angeles, California

Use commas to set off short statements or questions at the end of sentences:

My parents are giving me a new computer for my birthday, I hope.

Use commas to separate a quotation from the words that identify the source of the quotation:

In a speech in the Senate in 1847, John Calhoun said, "The surrender of life is nothing to sinking down into acknowledgement of inferiority."

However, you do not use a comma if the quotation is preceded by the word "that" or is only part of a quotation:

In one of her poems, Emily Dickinson compared the way the sun rose to a "Ribbon at a time."

Use commas in numbers (of four or more digits) and between the words for the day, month, and year of a date:

1,600 bottles of ketchup
December 26, 1997