In short, commas divide. They set apart elements such as words, phrases, and clauses from other elements in a sentence in order to show which words belong together. Paradoxically, by dividing elements, they also join elements. This is because the words set off, or set apart, by commas become a unit.
Curriculum
Course I: Writing Correctly
Module I: Punctuation
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- Commas -
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- Semicolons -
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- Colons -
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- Dashes -
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Apostrophes
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- Punctuation Review -
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Module II: Sentence Problems
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- Fragments -
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- Run-on Sentences -
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- Subject-Verb Agreement -
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- Dangling Modifiers -
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- Parallel Construction -
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- Sentence Problems Review -
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Module III: Words That Are Similar and Often Confused
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Final Course I Review
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Text lesson
Commas
This section focuses on commas and how they are used to separate four different elements in a sentence. Commas can:
– Separate clauses in compound sentences.
– Set apart introductory words, phrases, and clauses from the main clause.
– Separate words, phrases, and clauses in a series.
– Set apart parenthetical and nonessential material from the essential information of a sentence.
To complete this section, review each of the tabbed areas below and complete the Commas Self Check at the end.
Section I: Commas in Compound Sentences
Introduction
We will first review how commas work in compound sentences. Do you recall from school what a compound sentence is? Let’s see if you remember.
Review the multiple choice below and mentally select one of these definitions.
A compound sentence is…
A. a sentence with more than two phrases.
B. a sentence with two subjects and two verbs.
C. a sentence with two independent clauses, connected by “and,” “but,” or “or.”
D. a sentence broken in half, like a compound fracture.
NOW, CHECK YOUR ANSWER TO THE QUESTION POSED ABOVE
If you said “C”—a sentence with two independent clauses, connected by “and,” “but,” or “or”—you are right!
Looking at this a different way, if you removed “and,” “but,” or “or” from a compound sentence, you would have two clauses that could stand on their own as complete sentences. This is why they are considered “independent” clauses.
If you didn’t correctly select the definition of a compound sentence, don’t worry. Just ensure you feel comfortable with the definition of a compound sentence before reviewing the upcoming slideshow.
A Refresher on Clauses
Another term you will want to review before diving further into this section is “clause.”
A clause is a group of words that includes a subject and a verb.
Via the presentation that follows, you will review how commas separate independent clauses in compound sentences.
Presentation
Carefully review the presentation below, which further explains commas in compound sentences .
PRESENTATION TRANSCRIPT
As we reviewed a moment ago, compound sentences have two clauses, each of which can stand alone. However, the clauses are put into the same sentence because they are closely related.
This is a compound sentence:
The association recommended a change in procedures, but the director chose to ignore the recommendation.
A comma should precede the and, but, or or in compound sentences to signal readers that a new independent clause is beginning. In this case, the first independent clause is “The association recommended a change in procedures” because it can stand alone as a sentence. The second independent clause is “the director chose to ignore the recommendation” because it too can stand alone as its own sentence.
The word but is a coordinating conjunction in this case, and its purpose is to combine two independent clauses to create the compound sentence.
Using what you just learned about commas in compound sentences, is a comma required in any of the following sentences? Mentally select YES or NO.
Net farm income in California was down about 3 percent to just under $6 billion but land values were up an average of 5 percent statewide.
The board and management had established an internal credit review to strengthen internal controls and prevent weaknesses in operations.
Young, Beginning, and Small Farmer programs can be conducted on a safe and sound basis and system institutions should increase the coordination of YBS programs with other governmental agencies.
How did you do?
New farm income in California was down about 3 percent to just under $6 billion, but land values were up an average of 5 percent statewide.
YES: This compound sentence requires a comma before “but” to separate the two independent clauses, as shown above.
The board and management had established an internal credit review to strengthen internal controls and prevent weaknesses in operations.
NO: This simple sentence has only one clause. It has a dual subject, “board and management,” and a verb, “had established.”
Young, Beginning, and Small Farmer programs can be conducted on a safe and sound basis, and system institutions should increase the coordination of YBS programs with other governmental agencies.
YES: This compound sentence requires a comma before “and” to separate the two independent clauses, as shown above.
[Remember to go back to the top and use the Tabbed Navigation to travel to the next section.]
Section II: Commas Set Off Introductory Words, Phrases, and Clauses from the Main Clause
Introduction
Commas are required to set apart introductory words, phrases, and subordinate clauses from the main clause. Are you familiar with each of these things? Let’s do a brief review.
Introductory words include one-word modifiers and transitional devices. Some of the most common introductory words are shown in the table below.
INTRODUCTORY WORDS
| Moreover | However |
| Generally | Furthermore |
| Also | Coincidentally |
| Therefore | Unfortunately |
| Typically | Subsequently |
| Thus | Consequently |
INTRODUCTORY PHRASES
Introductory phrases are almost identical to introductory words but include a sequence of words rather than a single word at the beginning of a sentence. Here are some commonly used introductory phrases.
| In addition | In fact |
| In other words | Having said that |
| On the other hand | In contrast |
SUBORDINATE CLAUSES
The final element we’ll review is a subordinate clause. Unlike an independent clause, a subordinate clause cannot stand alone (by itself). In fact, it must be joined to an independent clause to make sense. You can identify these clauses by their starting words, some examples of which are shown in the table below.
| Although | While |
| If | When |
| Since | Because |
Now that we’ve reviewed introductory words, phrases, and subordinate clauses, view the slideshow below to learn about the role of commas in these elements.
Presentation
View the presentation below. Core details on the above content are explained in further detail, along with relevant examples.
PRESENTATION TRANSCRIPT
The role of commas in introductory words is simple: a comma always follows an introductory word. Here is an example.
The association recommended a change in procedure, but the director chose to ignore the recommendation.
You can hear the natural pause that happens when people use introductory words such as “however,” “therefore,” and “consequently” while speaking. Therefore, we use a comma to mirror this natural pause when writing.
Unlike introductory words, using a comma after an introductory phrase is optional. This is especially true if the introductory phrase is very short, as in this example.
In an earlier report the writer noted a change to the document.
The same sentence could be written with a comma:
In an earlier report, the writer noted a change to the document.
Both are correct, so you may choose which you prefer.
In some cases, introductory phrases will include a gerund or infinitive. When this happens, a comma is always used.
A gerund is the “-ing” form of a verb used at the beginning of a sentence, as underlined in the example below.
Responding to the Director’s request, the agency began its audit.
You can see how the introductory phrase is followed by a comma.
The infinitive form of a verb is written in the format “to _____.” Examples of infinitives are to complete, to find, to establish, and so on. The infinitive is underlined in the example below.
To determine the grantees, the organization held a meeting with its top members.
Again, you can see that the introductory phrase is followed by a comma.
In some cases, transitional words and phrases like those we’ve just covered are present in the middle of sentences instead of at the beginning. Here are two examples to demonstrate:
ICC still has regulatory responsibility, however, for balancing the needs of railroads and shippers.
There are, in fact, several options open to the agency.
As you can see, a comma both precedes and follows the transitional word and transitional phrase.
In addition to introductory (or transitional) words and phrases, commas are also required for introductory subordinate clauses. You’ll recall that a subordinate clause cannot stand on its own.
Here are three examples of introductory subordinate clauses with proper punctuation.
Although the mayor of the town was absent, the event continued as planned.
When the economy began to decline, many people lost their homes.
Because of the drought in the cotton region, prices of cotton shirts soared exponentially.
You’ll recognize the beginning words (i.e. although, when, because) from the chart we provided earlier. Introductory subordinate clauses are always followed by a comma.
Although a comma is required after an introductory subordinate clause, a subordinate clause at the end of a sentence is NOT preceded by a comma.
Incorrect: Inadequate soil compaction has increased operation and maintenance costs, because canals have rapidly deteriorated.
Correct: Inadequate soil compaction has increased operation and maintenance costs because canals have rapidly deteriorated.
Section III: Commas Separate Words, Phrases, and Clauses in a Series
Introduction
This is perhaps the most familiar usage of commas—and the simplest as well. Commas separate elements in a series, whether those elements are words, phrases, or clauses. Here is an example of each.
Words:
We interviewed key officials at the federal, state, and local levels.
Phrases:
The programs were selected because they are repetitive in nature, similar in operation, and national in scope.
Clauses:
The Director argued that his assistant, who hadn’t been seen since lunch, who had already taken four weeks of vacation, and who had done a very poor job on his last report, ought to be counseled.
View the presentation that follows to review further details on commas used in series.
Presentation
View the presentation below. Core details on the above content are explained in further detail, along with relevant examples.
PRESENTATION TRANSCRIPT
One issue regarding words in a series is whether a comma is required before the final word in the series.
Which sentence is appropriate:
The secretary placed the files, folders, disks, and keys in the safe.
Or:
The secretary placed the files, folders, disks and keys in the safe.
Both are correct, but in business writing the final comma before the last word in the series is more appropriate.
You may occasionally hear the final comma referred to as an “Oxford comma.” Below is another example.
Acceptable (less formal without an Oxford comma):
We reviewed all of the documents for the program. These included the introductory PDFs, the reviewer pledges, the strategy Excel files and the scoring documents.
Better (more formal with an Oxford comma):
We reviewed all of the documents for the program. These included the introductory PDFs, the reviewer pledges, the strategy Excel files, and the scoring documents.
Section IV: Commas Set Off Parenthetical Expressions and Nonessential Information from the Essential Information of a Sentence
Introduction
The final use of commas involves parenthetical expressions, which are short comments that provide explanatory but nonessential information. These parenthetical remarks can be removed from a sentence without changing the meaning of the sentence or its proper grammatical structure
Consider the following example.
The new procedure will not, in and of itself, cure the disease.
The parenthetical phrase in and of itself is nonessential material; it could be deleted and the message would be essentially unchanged. In such cases, the parenthetical information is preceded by a comma and followed by a comma.
Here is another example:
The ceiling of the Sistine Chapel, painted from 1508 to 1512, was one of Michelangelo’s greatest achievements.
The parenthetical expression painted from 1508 to 1512 gives extra details that are interesting but not crucial for understanding.
Discover how to punctuate parenthetical expressions using commas by viewing the presentation below.
Presentation
Carefully review the presentation below. Core details on the above content are explained in further detail, along with relevant examples.
PRESENTATION TRANSCRIPT
As you observed in the section introduction, commas should be used to set apart parenthetical expressions from the rest of the sentence, as in this sentence:
The staff was aware, through a written notice, that the Finance Department was conducting an audit of the direct payment procurement process.
One comma should precede a parenthetical expression, and another should follow it.
Thus far, we’ve covered general parenthetical expressions and their punctuation.
Now we are going to address a related issue involving commas: the difference between nonrestrictive clauses and restrictive clauses.
Remember the definition of a clause is: a group of words with a subject and a verb.
First, let’s explore nonrestrictive clauses. Like other parenthetical comments, nonrestrictive clauses add nonessential information to a sentence, such as in this example:
The chairman, who was elected by the board, determined that the policy violated the association’s bylaws.
The meaning of the sentence would not change if the clause who was elected by the board were omitted. The clause doesn’t restrict the meaning—hence, the term nonrestrictive clause.
And here is the relevance to punctuation: Nonrestrictive clauses are set off by commas. If the clause can be omitted, put commas around it.
Restrictive clauses, on the other hand, include essential information that restricts (limits) the noun that they refer to. The information in a restrictive clause is essential for the intended meaning of the sentence. For example:
The account executives who misrepresented the product’s safety record were dismissed.
The clause who misrepresented the product’s safety is essential to the meaning of the sentence because it limits the dismissal only to those account executives who misrepresented the product’s safety.
Here is another example of a restrictive clause:
The current system identifies nonimmigrants who have apparently overstayed their authorized period of admission.
The dependent clause above who have apparently overstayed their authorized period of admission [italics] restricts the meaning of nonimmigrants and distinguishes these nonimmigrants from others.
Note that restrictive clauses are NOT set off by commas.
To further emphasize the difference between nonrestrictive and restrictive clauses, consider the difference in meaning between:
Auditors, who use computers, make few mistakes.
Auditors who use computers make few mistakes.
In the first sentence, the clause is nonrestrictive (i.e., it doesn’t restrict the meaning of auditors). It’s stating that auditors make few mistakes and that auditors use computers.
In the second sentence, the clause is restrictive because it limits the word auditors to specific auditors—those who use computers. The sentence means specifically those auditors who use computers make few mistakes.
Nonrestrictive and restrictive clauses bring up the which/that grammatical controversy. Should a clause begin with “which” or “that?” Here are the rules.
Use “that” in restrictive clauses.
Use “which” in nonrestrictive clauses.
This sentence demonstrates the use of that in a restrictive clause:
The INS cannot realistically implement control mechanisms that provide the degree of precision required by the legislation.
This sentence demonstrates the use of which in a nonrestrictive clause:
If the military finance centers can now handle the volume of transactions, which could be as high as two million during a legislative adjustment, then the VA can easily accomplish necessary programming.
To summarize the differences between nonrestrictive and restrictive clauses:
Nonrestrictive = nonessential information, set off by commas, use which.
Restrictive = essential information, NOT set off by commas, use that.
Final Recap: Commas
As you learned in this section, commas can separate the following elements in a sentence:
– Clauses in compound sentences
– Introductory words, phrases, and clauses from the main clause
– Words, phrases, and clauses in a series
– Parenthetical expressions, including nonrestrictive clauses.
Now, test your knowledge by completing the Commas Self Check.