2. Purdue University Writing Lab
What Is a Comma?Clauses
and Phrases
A comma is a
punctuation mark
that indicates a
pause is needed in
a sentence.
Commas help to
clarify meaning for
the reader.
Conquering the Comma
3. Purdue University Writing Lab
Sentence Structure:
Independent Clause
A complete sentence has two
components, a subject and a
verb.
The subject and verb must
form a complete thought to
be considered an
independent clause.
The couple dances.The couple dances.
subject (S) verb (V)
Conquering the Comma
4. Purdue University Writing Lab
Sentence Structure:
Compound Sentence
A sentence that contains two
independent clauses joined
by a conjunction is called a
compound sentence.
A conjunction joins words,
phrases, and clauses
together in a sentence.
Conjunctions
for
and
nor
but
or
yet
so
FAN BOYS
Conquering the Comma
5. Purdue University Writing Lab
Sentence Structure:
Compound Sentence
The comma in a compound
sentence is placed before the
coordinating conjunction.
Andy built a snowman, and
Jeff played with his dog.
S V conj.
Andy built a snowman, and
Jeff played with his dog.
S V
Conquering the Comma
6. Purdue University Writing Lab
Where would you
place the comma in
the following
sentence?
Sentence Structure:
Compound Sentence
Dan struggled with his homework so his father helped him.Dan struggled with his homework, so his father helped him.
S V conj. S V
Conquering the Comma
7. Purdue University Writing Lab
Sentence Structure:
Dependent Clause
A dependent
clause contains a
subject and verb,
but the clause
cannot stand
independently.
Dependent clauses
can often be
identified by the
use of dependent
clause markers.
Some dependent clause markers:
because
since
when
while
until
if
as
though
although
unless
after
before
once
whether
Conquering the Comma
8. Purdue University Writing Lab
Sentence Structure:
Dependent Phrases and Clauses
Dependent phrases
and clauses help to
clarify and add detail
to an independent
clause.
Dependent clauses
may appear at the
beginning, middle, or
end of a sentence.
Conquering the Comma
9. Purdue University Writing Lab
Introductory clause=
dependent clause located at the beginning
of a sentence
When a dependent
clause is placed at the
beginning of a sentence,
place a comma between
the independent clause
and the dependent
clause.
When Elizabeth called 911, the firemen rushed to her rescue.When Elizabeth called 911, the firemen rushed to her rescue.
DCM S V S V
Conquering the Comma
10. Purdue University Writing Lab
Introductory Clause
Where would you place the comma in the
following examples?
After the movie ended we went out for coffee.
Since it was raining we decided to go to the movies.
Once the movie began I fell asleep.
Since it was raining, we decided to go to the movies.
DCM S V S V
Once the movie began, I fell asleep.
DCM S V S V
After the movie ended, we went out for coffee.
DCM S V S V
Conquering the Comma
11. Purdue University Writing Lab
Dependent Clauses
When a dependent clause is
located after an independent clause,
DO NOT place a comma between the two.
I went on the roller coaster because my brother dared me.
S V DCM S V
I became very sick when the
S V DCM
roller coaster zoomed upside down.
S V
Conquering the Comma
12. Purdue University Writing Lab
Notice the different?
Dependent clause BEFORE the
independent clause:
Because my brother dared me, I went on
the roller coaster.
Dependent clause AFTER the
independent clause:
I went on the roller coaster because my
brother dared me.
13. Purdue University Writing Lab
Sentence Structure:
Essential Phrases and Clauses
An essential clause or
phrase is used to modify
(or describe) a noun.
It also adds information
that is critical to the
meaning of the sentence.
Essential clauses are NOT
set off by commas.
Conquering the Comma
14. Purdue University Writing Lab
The people who work in my office are so uptight!
Sentence Structure:
Essential Phrases and
Clauses
S essential phrase V
Without the essential phrase, this sentence does not
make complete sense : The people are so uptight!
Conquering the Comma
15. Purdue University Writing Lab
The beverage that I had at Joe’s was much better than this one!
Sentence Structure:
Essential Phrases and Clauses
S essential V
The word “that” is almost always an indicator of an
essential phrase or clause.
Conquering the Comma
16. Purdue University Writing Lab
Sentence Structure: Nonessential
Phrases and Clauses
A nonessential phrase or clause (often
called an “appositive” adds extra
information to a sentence.
This information can be eliminated from
the sentence without jeopardizing the
meaning of the sentence.
Always place commas around
nonessential phrases and clauses.
Conquering the Comma
17. Purdue University Writing Lab
My brother, who lives across town, plans to throw a party!
S non-essential V
Even without the phrase the sentence still makes
sense : My brother plans to throw a party!
Sentence Structure: Nonessential
Phrases and Clauses
Conquering the Comma
18. Purdue University Writing Lab
Steve said that he would propose to me on
Valentine’s Day, which is my favorite holiday!
S V
non-essential
Use commas to set off additional information
Sentence Structure: Nonessential
Phrases and Clauses
Conquering the Comma
19. Purdue University Writing Lab
Would you place commas in the
following sentences? If so, where?
I am planning a trip to Paris
which is one of the greatest
cities in the world.
No comma is needed. The sentence is correct.
The place that I would most
like to see is the Eiffel Tower.
Pierre who is one of my
business contacts will meet
me at the airport.
I am planning a trip to Paris,
which is one of the greatest
cities in the world.
Pierre, who is one of my
business contacts, will meet
me at the airport.
Conquering the Comma
20. Purdue University Writing Lab
Sentence Structure:
Commas in a Series
Place commas in a sentence to
divide items in a list.
The commas will help the reader to
avoid confusion.
The comma before the conjunction
is generally required, but it can be
omitted if there is no possibility of
confusion.
Conquering the Comma
21. Purdue University Writing Lab
Sentence Structure:
Commas in a Series
Consider the difference in the following:
Last month, Alex dated Mary Ann Lee
and Kim.
Last month, Alex dated Mary, Ann, Lee,
and Kim.
Last month, Alex dated Mary Ann, Lee,
and Kim.
How many women did Alex date?
22. Purdue University Writing Lab
Commas should be placed in series of words,
phrases, or clauses.
Place commas in the following sentences:
Sentence Structure:
Commas in a Series
Martina brushed her hair put on
her pajamas and went to bed.
She fell asleep and dreamed that she was
a princess she kissed a frog and she
rescued her prince.
Martina brushed her hair, put on
her pajamas, and went to bed.
She fell asleep and dreamed that she was
a princess, she kissed a frog, and she
rescued her prince.
23. Purdue University Writing Lab
Commas with adjectives
Use commas to separate adjectives that
provide an equal description of a noun.
THE TEST:
Can you put “and” between the adjectives?
Can they be described in reverse order?
If so, use a comma.
big blue house three hungry kittens
a cranky, ungrateful man
24. Purdue University Writing Lab
A Common Comma Error:
The Comma Splice
A comma splice is an error in which two
independent clauses are joined by a comma.
We had a nice time, I hope we can meet again soon.
S V S V
The Internet has revolutionized the business world,
S V
online sales have increased dramatically this year.
S V
25. Purdue University Writing Lab
To Correct a Comma Splice
Insert a conjunction between the two independent
clauses.
Start a new sentence.
Insert a semi-colon between the two independent
clauses (only in cases where the independent clauses
are closely related in topic).
•We had a nice time, and I hope we can meet again soon.
•We had a nice time. I hope we can meet again soon.
•The Internet has revolutionized the business world; online
sales have increased dramatically this year.
26. Purdue University Writing Lab
How would you correct the
following sentences?
This semester I am taking calculus physics and economics.
Calculus is my best subject, I am certain I will get an A.
Although I am very busy I still find time to have fun.
Last weekend my brother visited me and we went to a
football game a party and a rock concert.
This semester I am taking calculus, physics, and economics.
Calculus is my best subject, and I am certain I will get an A.
Although I am very busy, I still find time to have fun.
Last weekend my brother visited me, and we went to a
football game, a party, and a rock concert.
27. Purdue University Writing Lab
Where can you go for additional help
with comma usage?
Purdue University Writing
Lab
Heavilon 226
Grammar Hotline:
(765) 494-3723
Check our web site:
http://owl.english.purdue.edu
Email brief questions:
owl@owl.english.purdue.edu
Purdue University Writing Lab
Key Concepts: The facilitator may choose to invite the audience to respond to the title question and allow participants to discuss the function of the comma. Many writers become frustrated with comma usage because they are unsure of where to place them in their sentences. This presentation is designed to demystify the placement and usage of commas.
The facilitator may stress to participants that commas should not be ignored in writing; they are often needed to clarify meaning within a sentence and can help to avoid confusion.
Click mouse after title question to reveal each response.
Key Concepts: This slide explains the structure of an independent clause, the primary building block for the development of any sentence. An independent clause requires a subject and a verb that can stand as a complete thought. Sentences can be very short, as the one detailed in the slide. The facilitator may ask the audience to identify the subject and verb in the example.
Click mouse after text appears to reveal picture and sample sentence.
Click mouse after sample sentence to reveal the labels “subject” and “verb.”
Key Concepts: This slide explains the structure of a compound sentence and the role of a conjunction. An easy method for remembering the seven coordinating conjunctions is the acronym “fan boys.”
Click mouse at the end of the first column.
Click mouse at the end of the conjunction list to reveal the acronym.
Example: This slide exemplifies the location of a comma in a compound sentence, before the coordinating conjunction. The facilitator may ask participants to identify the subjects, verbs, and conjunction in the example.
Click after example sentence appears to reveal parts of speech.
Example: This slide provides participants with an opportunity to locate the correct position for the comma within the sample sentence. The facilitator may also invite students to identify the subjects, verbs, and conjunction in the sentence.
Click mouse after sample sentence to reveal the comma.
Click mouse after the comma to reveal parts of speech.
Key Concepts: This slide explains the definition of a dependent clause. The dependent clause markers can help writers identify clauses that cannot stand alone within a sentence.
Key Concepts: This slide further clarifies the role of dependent phrases and clauses within a sentence.
Key Concepts: An introductory clause is a dependent clause located at the beginning of a sentence. After an introductory clause, a comma is needed to distinguish it from the independent clause.
Activity: The facilitator may choose to ask students to identify the independent and dependent clauses, the subjects, the verbs, and the dependent clause marker in the sample sentence.
Click mouse to reveal the parts of speech.
Activity: This interactive slide invites participants to place commas after the introductory clauses in each sentence. Again, the facilitator may ask students to identify the parts of speech in each example.
Click mouse to reveal parts of speech, and then click again to reveal each example.
Activity: When a dependent clause follows an independent clause, commas are not used. Facilitators may choose to ask students to identify the parts of speech in each example.
Key Concepts: This slide leads off a section about essential and non-essential phrases and clauses. Essential phrases and clauses—elements that add critical information to the meaning of a sentence—do not have commas placed around them.
Example: This example illustrates the placement of an essential phrase within a sentence. The phrase “who work in my office” is critical to the overall meaning of the sentence; therefore, it should not be set off with commas.
If the clause or phrase is eliminated from the sentence and the sentence no longer makes sense, the clause or phrase is essential.
Key Concept: The word “that” almost always indicates an essential phrase or clause.
Key Concepts: This slide illustrates the difference between essential and nonessential elements. While commas should not be placed around essential phrases and clauses, they should be placed around nonessential phrases and clauses.
Example: Nonessential phrases and clauses can be removed from sentences without jeopardizing the overall meaning of a sentence. In this example, “who lives across town” is superfluous information; it is not critical to the main message of the sentence—the woman’s brother will throw a party for her.
Example: This slide provides another example illustrating the placement of a nonessential phrase within a sentence. At the end of a sentence, the nonessential element should have a comma placed before it and a period after it. The facilitator may wish to stress that “which” often, but not always, indicates a nonessential phrase or clause.
Activity: These examples allow participants an opportunity to test their comma skills.
The first example needs a comma after “Paris” to set off the nonessential phrase.
The second example requires no comma. The phrase “that I would most like to see” is essential to the meaning of the sentence. The sentence will not make sense without this essential phrase.
The third example requires two commas, both before and after the nonessential phrase “who is one of my business contacts.” The main message of this sentence—that Pierre will meet this person at the airport—is clear without knowing the additional information about his identity.
Click to reveal the comma placement for each example.
Key Concept: Commas should be placed between each element within a list. This placement can help the reader to avoid confusion.
Activity: These examples illustrate the importance of comma placement within a list. The facilitator may ask students to answer the question “How many women did Alex date?” in accordance with each example—two women in the first, four in the second, and three in the third.
Click to reveal each example.
Activity: The facilitator may stress to participants that a series includes a list of words, but it can also include a list of phrases or clauses. This exercise allows participants to determine when the commas should be placed in each sentence.
Click to reveal commas for each sentence.
Key Concepts: Students often find comma placement between adjectives to be tricky. The key is to determine if the adjectives are equal—meaning that they modify the noun in the same capacity. Adjectives of size and quantity are generally considered to be unequal to adjectives of character or quality. Placing “and” between adjectives or reversing the order of adjectives are good tests to determine if a comma is needed.
Key Concepts: One of the most prevalent comma errors is the comma splice—the placement of a comma between two independent clauses.
Key Concepts: This slide enumerates several methods for correcting comma splices. The examples listed here are corrections of the comma splices in the previous slide.
Activity: This slide invites participants to again test their comma skills.
The first example requires commas between each element within the list.
The second example contains a comma splice. The sentence may be corrected by the addition of a conjunction after the comma, turning the comma splice into a compound sentence. This example may also be corrected by separating the two clauses into two separate sentences, or by changing the comma to a semi-colon.
The third example requires a comma after the introductory clause. The facilitator may wish to note that “although” is a dependent clause marker.
The fourth example, a compound sentence, requires a comma before the conjunction. Commas are also needed after each element in the list.
Click mouse to reveal comma placement for each example.
Rationale: As the presentation concludes, the facilitator can remind students that they can come to the Writing Lab for extra help with comma usage.
Click mouse after the title question.
For additional assistance with comma usage, see:
Harris, Muriel. Prentice Hall Reference Guide to Grammar and Usage. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2000.
