Overview: Commas
The comma is the most frequently used punctuation mark, but it is also the most often misused. Commas make reading sentences easier because they separate the parts of sentences.
Commas with Independent Clauses
Use a comma before the coordinating conjunctions and, but, for, nor, or, so, and yet when they join two independent clauses. (Remember that an independent clause must have both a subject and a verb.)
Independent clauses: The instructor put us in small groups , and she gave us a new assignment.
Independent clauses: The essay was difficult to read , but I learned some new vocabulary words.
Hint: Do not use a comma when a single subject has two verbs.
Single subject: The instructor put us in small groups and gave us a new assignment.
The coordinating conjunction (and ) joins two verbs, but not two independent clauses. Only if the second verb has its own subject should you add a comma.
Independent clauses: The instructor put us in small groups , and she gave us a new assignment.
Each verb has its own subject, so and joins two independent clauses. Notice the comma.
Commas with Items in a Series
Use commas to separate items in a series of items joined by a coordinating conjunction. This means that you should put a comma between all items in a series.
Series of nouns: The class required that we read two novels , twenty short stories , and twelve poems.
Series of verbs: The students exchanged their essays , read them , and gave each other suggestions.
Notice the comma before and in each series.
Commas with Introductory Words
Use a comma to set off an introductory word, phrase, or clause from the rest of its sentence. If you are unsure whether to add a comma, try reading the sentence with your reader in mind. If you want your reader to pause after the introductory word or phrase, you should insert a comma.
Introductory word: Actually, the class was more interesting than I thought it would be.
Introductory phrase: To save time, I did my homework during my lunch break.
Introductory clause: When the professor wrote on the board, we began taking notes.
Commas with Coordinate Adjectives
Sometimes adjectives in a series preceding a noun need commas, but sometimes they do not. Look at these two examples.
Adjectives with commas: The long, boring lecture is finally over. Adjectives without commas: Three new Spanish novels were checked out of the library.
The first example has a series of coordinate adjectives—that is, the adjectives both modify the noun equally. In this case, both adjectives are descriptive. The second example has a series of cumulative adjectives —adjectives that combine to modify the noun as a whole. In this case, the three adjectives together modify the noun.
So how do you know whether or not to use commas? You can use one of two tests. One test is to insert the word and between the adjectives. If the sentence makes sense, use a comma. Another test is to switch the order of the adjectives. If the sentence still reads clearly, use a comma between the two words.
Test 1: The long and boring lecture is finally over. OK, so use a comma
Test 2: The boring, long lecture is finally over. OK, so use a comma Test 1: Three and new and Spanish novels were checked out of the library. NO comma
Test 2: Three Spanish new novels were checked out of the library. NO comma Commas with Interrupters
Use a comma before and after a word or phrase that interrupts the flow of a sentence. These interrupters are not necessary for understanding the main point of a sentence. So setting them off makes it easier for readers to recognize the main point.
Appositives
Appositives are words or phrases that identify, or could replace, another element in a sentence. Appositives are put next to the word that they identify.
If an appositive is essential to the meaning of a sentence, do not put commas around it. If an appositive just adds optional information, it is nonrestrictive . Put commas around nonrestrictive words and expressions to show the reader that the information is not essential to the meaning of the sentence. Look at the following examples.
Nonrestrictive appositive: Amy's brother , Joseph, is studying engineering.
(Amy has just one brother.)
Essential appositive: Amy's brother Joseph is studying engineering. (Amy has more than one brother.)
Nonrestrictive Clauses
A very common type of interrupter is a clause that begins with who, whose, which, when, or where and is not necessary for understanding the main point of the sentence. These clauses are known as nonrestrictive clauses because they do not restrict, or limit, the meaning of the sentence.
Nonrestrictive clause: The new instructor , who came here from UC Berkeley,
is teaching the American literature class.
Because the information "who came here from UC Berkeley" is not necessary for understanding the main idea of the sentence, the clause is set off with commas.
Nonrestrictive clause: The public library, which is downtown, provides many DVDs.
The main point here is that the public library provides DVDs. Since the other information isn't necessary to understanding the sentence, the clause is set off with commas.
Hint: Do not use commas with who, whose, which, when, or where if the information is necessary for understanding the main point of the sentence. Essential clause: The man who is running for office shook my hand. The information in the who clause is necessary to understanding which man did the hand shaking. So the clause is not set off with commas.
Hint: Do not use commas to set off clauses beginning with that. Clauses beginning with that always give essential information.
Essential clause: The movie theater that is on Elm Street is showing Jurassic Park III.
Transitional and Parenthetical Words and Expressions Transitional words and expressions link sentences and paragraphs together. Parenthetical words and expressions add comments to a sentence. Put commas around transitional and parenthetical words and expressions. Look at the following examples.
Transitional word: I knew the exam would be hard. I didn't study for it, however, because I had to work late.
Parenthetical phrase: The city with the most hotels, according to this travel journal, is Las Vegas.
Commas in Dialogue
Use commas to mark direct quotations. A direct quotation records a person's exact spoken or written words. Commas set off the exact words
from the rest of the sentence, making it easier to understand who said what. Notice the use of commas in the following examples.
Direct quotation: The instructor said, "The exam will be next Friday." Direct quotation: "The exam will be next Friday," the instructor said. Direct quotation: "The exam," said the instructor , "will be next Friday." If a person is addressed directly, use a comma after the person's name. Direct address: "Professor Williams, here is my revised paper," the student said.
Hint: If a quotation ends with a question mark or an exclamation point, do not use a comma. Only one punctuation mark is needed.
Not: "What was the question?, " he asked.
Correct: "What was the question?" he asked.
Other Uses of Commas
Other commas clarify information in everyday writing.
Numbers: What is 2,667,999 divided by 10,300?
Dates: Mike and Melissa were married on August 1, 2000, in Cincinnati. (Notice that there is a comma both before and after the year.)
Addresses: Nicole moved from Lamont, California, to 8900 New Fork Lane, Aspen, CO 81612.
(Notice that there is no comma between the state and the zip code.) States: They moved from San Antonio, Texas, to Phoenix, Arizona. (Notice that there is a comma both before and after a state.) Letters: Dear Alyson, Yours truly,
Unnecessary Commas
Avoid using commas in the following situations.
Between a Subject and Verb
Not: The girl who baked the cookies, brought them to class.
Correct: The girl who baked the cookies brought them to class. Between a Verb and Its Object
Not: The applicant sent, a gracious thank-you letter .
Correct: The applicant sent a gracious thank-you letter.
Between Pairs of Words, Phrases, or Clauses Joined by a Coordinating Conjunction
Not: The manager was successful in looking for, and hiring a new employee. Correct: The manager was successful in looking for and hiring a new employee.
After a Conjunction (and, but, because, although, and so on)
Not: The new owners were pleased with their pets, and, the pets were happy too.
Correct: The new owners were pleased with their pets, and the pets were happy too.
Overview and Help Me Answer This adapted from Mosaics: Focusing on Sentences in Context by Kim Flachmann.
Overview: Commas
The comma is the most frequently used punctuation mark, but it is also the most often misused. Commas make reading sentences easier because they separate the parts of sentences.
Commas with Independent Clauses
Use a comma before the coordinating conjunctions and, but, for, nor, or, so, and yet when they join two independent clauses. (Remember that an independent clause must have both a subject and a verb.)
Independent clauses: The instructor put us in small groups , and she gave us a new assignment.
Independent clauses: The essay was difficult to read , but I learned some new vocabulary words.
Hint: Do not use a comma when a single subject has two verbs.
Single subject: The instructor put us in small groups and gave us a new assignment.
The coordinating conjunction (and ) joins two verbs, but not two independent clauses. Only if the second verb has its own subject should you add a comma.
Independent clauses: The instructor put us in small groups , and she gave us a new assignment.
Each verb has its own subject, so and joins two independent clauses. Notice the comma.
Commas with Items in a Series
Use commas to separate items in a series of items joined by a coordinating conjunction. This means that you should put a comma between all items in a series.
Series of nouns: The class required that we read two novels , twenty short stories , and twelve poems.
Series of verbs: The students exchanged their essays , read them , and gave each other suggestions.
Notice the comma before and in each series.
Commas with Introductory Words
Use a comma to set off an introductory word, phrase, or clause from the rest of its sentence. If you are unsure whether to add a comma, try reading the sentence with your reader in mind. If you want your reader to pause after the introductory word or phrase, you should insert a comma.
Introductory word: Actually, the class was more interesting than I thought it would be.
Introductory phrase: To save time, I did my homework during my lunch break.
Introductory clause: When the professor wrote on the board, we began taking notes.
Commas with Coordinate Adjectives
Sometimes adjectives in a series preceding a noun need commas, but sometimes they do not. Look at these two examples.
Adjectives with commas: The long, boring lecture is finally over. Adjectives without commas: Three new Spanish novels were checked out of the library.
The first example has a series of coordinate adjectives—that is, the adjectives both modify the noun equally. In this case, both adjectives are descriptive. The second example has a series of cumulative adjectives —adjectives that combine to modify the noun as a whole. In this case, the three adjectives together modify the noun.
So how do you know whether or not to use commas? You can use one of two tests. One test is to insert the word and between the adjectives. If the sentence makes sense, use a comma. Another test is to switch the order of the adjectives. If the sentence still reads clearly, use a comma between the two words.
Test 1: The long and boring lecture is finally over. OK, so use a comma
Test 2: The boring, long lecture is finally over. OK, so use a comma Test 1: Three and new and Spanish novels were checked out of the library. NO comma
Test 2: Three Spanish new novels were checked out of the library. NO comma Commas with Interrupters
Use a comma before and after a word or phrase that interrupts the flow of a sentence. These interrupters are not necessary for understanding the main point of a sentence. So setting them off makes it easier for readers to recognize the main point.
Appositives
Appositives are words or phrases that identify, or could replace, another element in a sentence. Appositives are put next to the word that they identify.
If an appositive is essential to the meaning of a sentence, do not put commas around it. If an appositive just adds optional information, it is nonrestrictive . Put commas around nonrestrictive words and expressions to show the reader that the information is not essential to the meaning of the sentence. Look at the following examples.
Nonrestrictive appositive: Amy's brother , Joseph, is studying engineering.
(Amy has just one brother.)
Essential appositive: Amy's brother Joseph is studying engineering. (Amy has more than one brother.)
Nonrestrictive Clauses
A very common type of interrupter is a clause that begins with who, whose, which, when, or where and is not necessary for understanding the main point of the sentence. These clauses are known as nonrestrictive clauses because they do not restrict, or limit, the meaning of the sentence.
Nonrestrictive clause: The new instructor , who came here from UC Berkeley,
is teaching the American literature class.
Because the information "who came here from UC Berkeley" is not necessary for understanding the main idea of the sentence, the clause is set off with commas.
Nonrestrictive clause: The public library, which is downtown, provides many DVDs.
The main point here is that the public library provides DVDs. Since the other information isn't necessary to understanding the sentence, the clause is set off with commas.
Hint: Do not use commas with who, whose, which, when, or where if the information is necessary for understanding the main point of the sentence. Essential clause: The man who is running for office shook my hand. The information in the who clause is necessary to understanding which man did the hand shaking. So the clause is not set off with commas.
Hint: Do not use commas to set off clauses beginning with that. Clauses beginning with that always give essential information.
Essential clause: The movie theater that is on Elm Street is showing Jurassic Park III.
Transitional and Parenthetical Words and Expressions Transitional words and expressions link sentences and paragraphs together. Parenthetical words and expressions add comments to a sentence. Put commas around transitional and parenthetical words and expressions. Look at the following examples.
Transitional word: I knew the exam would be hard. I didn't study for it, however, because I had to work late.
Parenthetical phrase: The city with the most hotels, according to this travel journal, is Las Vegas.
Commas in Dialogue
Use commas to mark direct quotations. A direct quotation records a person's exact spoken or written words. Commas set off the exact words
from the rest of the sentence, making it easier to understand who said what. Notice the use of commas in the following examples.
Direct quotation: The instructor said, "The exam will be next Friday." Direct quotation: "The exam will be next Friday," the instructor said. Direct quotation: "The exam," said the instructor , "will be next Friday." If a person is addressed directly, use a comma after the person's name. Direct address: "Professor Williams, here is my revised paper," the student said.
Hint: If a quotation ends with a question mark or an exclamation point, do not use a comma. Only one punctuation mark is needed.
Not: "What was the question?, " he asked.
Correct: "What was the question?" he asked.
Other Uses of Commas
Other commas clarify information in everyday writing.
Numbers: What is 2,667,999 divided by 10,300?
Dates: Mike and Melissa were married on August 1, 2000, in Cincinnati. (Notice that there is a comma both before and after the year.)
Addresses: Nicole moved from Lamont, California, to 8900 New Fork Lane, Aspen, CO 81612.
(Notice that there is no comma between the state and the zip code.) States: They moved from San Antonio, Texas, to Phoenix, Arizona. (Notice that there is a comma both before and after a state.) Letters: Dear Alyson, Yours truly,
Unnecessary Commas
Avoid using commas in the following situations.
Between a Subject and Verb
Not: The girl who baked the cookies, brought them to class.
Correct: The girl who baked the cookies brought them to class. Between a Verb and Its Object
Not: The applicant sent, a gracious thank-you letter .
Correct: The applicant sent a gracious thank-you letter.
Between Pairs of Words, Phrases, or Clauses Joined by a Coordinating Conjunction
Not: The manager was successful in looking for, and hiring a new employee. Correct: The manager was successful in looking for and hiring a new employee.
After a Conjunction (and, but, because, although, and so on)
Not: The new owners were pleased with their pets, and, the pets were happy too.
Correct: The new owners were pleased with their pets, and the pets were happy too.
Overview and Help Me Answer This adapted from Mosaics: Focusing on Sentences in Context by Kim Flachmann.