In English, conventions of punctuation are closely tied to language structure. So it's helpful to ask yourself if you are separating or combining information. If not, you probably don't need a comma. If so, what you want to do probably falls into one of the categories discussed on this page.
Commas that separate information in the middle of a sentence work in pairs. That is, you need two of them, one before and one after the information you're separating (usually from the main idea). In the examples below, we've used the terms you'll find in the The Holt Handbook in case you want more information about rules.
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Tag Elements are found in questions. The helping verb, which is repeated in order to construct the question, is separated from the main sentence with a single comma. The second comma in this pair is replaced by the question mark at the end of the sentence.
Carmen will go, won't she?
Nat is happy today, isn't he?
Commas separate tag elements from the rest of the sentence.
Direct questions included in a sentence are set off by commas:
Should I, the student asked himself, do my laundry or study for my test?
The student asked himself, should I study for my test or go to the frat party?
Indirect questions are not set off from the rest of the sentence:
The student asked herself whether she should write her paper or go to the sorority party.
Whether she should do her laundry or write her paper was the question the student asked herself.
Because these elements are non-essential, they (words, phrases, or even clauses) interrupt the flow of thought by shifting the reader's attention to other information for just a bit. Sometimes, writers include such asides in parentheses, but too many parentheses in a text can distract the reader. To avoid losing your reader's attention, consider using commas to set off the parenthetical comment, instead:
Separate parenthetical elements with paired (that is, before
and after) commas. The phrase "in a way" is set off by
commas in the example above. This allows the writer to share an
aside. Below, we've provided information and examples on 3 other
types of parenthetical elements, all of which are nonrestrictive.
Jack the Ripper, who has a nasty reputation, has not been invited to the party.
An appositive is another type of modifier that can be used parenthetically. An appositive re-names some noun in the sentence:
Dr. William Muse, the former president of Auburn University, shook every graduate's hand.
The former president of Auburn University, Dr. William Muse, shook every graduate's hand.
In the first sentence, "the president of Auburn University" is an appositive renaming the subject of the sentence, Dr. William Muse. In the second sentence, the modifying expression is "Dr. William Muse."
Commas separate the appositive from the rest of the sentence.
Transitional elements are another type of parenthetical. These give readers information about how ideas in paragraphs are connected. We use commas to separate these elements from the main sentence they appear in.
Most importantly, we're all looking forward to Spring Break.
But summer vacation is welcome, too.
I want to remind you, first of all, of the importance of voting.
Commas separate the transitional element from the rest of the sentence.
Contrasting elements also provide parenthetical information:
Students may focus on the cost of health care, not their health, when deciding to see a doctor.
Commas separate the contrasting element from the rest of the sentence.
Commas are used to separate two or more adjectives when they modify the same noun:
Equal communication is intrinsic to providing dependable, inexpensive care.
In this sentence, the meaning the comma implies is that the
care is both dependable and inexpensive.
This one gets tricky. Why? Some writers (like newspaper journalists) omit the comma before the conjunction. However, this sometimes leads to trouble:
We want bologna, cheese and peanut butter sandwiches.
You'll probably read this as a request for 3 different sandwiches, but grammatically, it's reasonable for a reader to interpret this as a request for 2 kinds of sandwiches: one bologna sandwich and one made with cheese and peanut butter. Unless you want to risk eating cheese with peanut butter, you'll want to include that comma before the conjunction:
We want bologna, cheese, and peanut butter sandwiches.
In formal and academic writing, convention requires the comma before the conjunction:
All administrators, faculty, and students should report to the auditorium by 6:00.
Additional concerns that make this tricky:
No comma separates the first or last item in the list from the rest of the sentence: We wouldn't put a comma before "bologna" or after "butter."
We want bologna, cheese, and (,) peanut butter sandwiches.
Sometimes writers change the normal word order in a sentence. You can establish a less formal, spoken tone by
placing an element normally found at the end of the sentence at
the beginning:
I don't like donuts; bagels, I like
Bad guys always lose, but John Wayne, he always wins.
Movement of information is also used for emphasis. Here, participle phrases are fronted:
Thinking he was right, Elroy insisted on the answer.
Confused by the headlights, the deer stood frozen in the road.
Because it was raining, I took my umbrella.
Merrily, we roll along.
In fact, I wanted two of them.
When you preface a comment with someone's name, you've used a noun of address. Nouns of address are separated from the rest of the sentence with a comma:
Kim, we're really proud that you won first prize.
Commas separate the quotation from the rest of the sentence:
Pat whined, "But you said I could."
"Don't whine," snapped Pat's mother.
"But you really did say we could," whispered Arthur, "the other day at the pool."
There are two formats for writing dates, military style and civilian style. Military style does not require commas.
31 DEC 98
In the more common style the order of the elements is month, day, year. According to convention, when all three elements appear in a sentence, the year is set off by commas.
The new millennium will not begin until January 1, 2001, according to some.
When fewer than three of the elements occur, no comma is used.
The new millennium begins January 2001.
The new millennium begins January 1.
When the name of a day accompanies a date, the second element is treated as an appositive.
This year Thanksgiving falls on Thursday, November 26, during the last full week of the month.
This year Thanksgiving falls on November 26, Thursday, during the last full week of the month.
Sometimes a comma is necessary to prevent misreadings. The words "woman without her man is savage" have different meanings depending on where we put the commas.
Woman: without her, man is savage. (Note the use of the colon in this sentence.)
Woman, without her man, is savage.
Here's another example:
The pitcher beaned the batter who mouthed off at him and swore.
In this sentence the batter did the swearing. In the next sentence, the pitcher does the swearing:
The pitcher beaned the batter who mouthed off at him, and swore.
Commas are also used to separate identical or similar elements to avoid ambiguity:
They tried their consumes on, on Sunday.
Whatever is, is.
In the year 2000, 2000 doves will be released.
BEWARE THESE PITFALLS If you include commas that aren't necessary, you can confuse your reader. Consider the following pitfalls when trying to decide whether you need a comma or not:
The Senate Sub-Committee for Indian Affairs decided that the government should give control of Indian programs to the tribes.
A comma after "Affairs" might seem like a good ideas but would separate the subject from the predicate.
The problem was he didn't want to go to class.
A comma after "was" might seem appropriate but would separate the linking verb from the subject predicative.
Commas that combine are used when you connect 2 sentences.
Peter washed the dishes, and Maria changed the oil in the car.
Questions or comments? Got a great sentence to share? E-mail us!
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