Punctuation is one component of writing that people seldom think about or notice -- except when it is wrong. At their worst, misused punctuation marks -- commas, semicolons, quotation marks, and the rest -- may muddle the meaning of your sentences, leaving your reader confused and frustrated. Even less egregious errors -- say, a missing or misplaced apostrophe -- can give your written work an appearance of carelessness and lack of attention.
Purdue University's Online Writing Lab has an excellent section on punctuation of all kinds. It would be a good investment of time to refresh your memory with the explanations and practice exercises found on that site. Here, though, are brief discussions of some of the most common punctuation errors.
Quotation marks are required whenever you are giving the exact words spoken or written by another person. In American English, double quotation marks are used for indicating quotations. Single quotation marks indicate a quote within a quote:
Prof. McArdle said, "The briefs will be due on Tuesday."
Loucas said, "Prof. McArdle said, 'The briefs will be due on Tuesday.'"
(For those of you familiar with British English conventions, this is a change in style.)
The rules for using other punctuation with quotation marks are fairly straightforward. If you are introducing a quote with a phrase such as "He said," "The record states," or "As Justice Scalia wrote," you must use a comma before the quotation marks:
The defense attorney shouted, "I object to that question!"
If you want to introduce a quote with an independent clause (a phrase that could stand alone as its own sentence), you must use a colon before the quotation marks:
The defense attorney raised an objection: "That question is not relevant!"
If, however, you are integrating quoted material within your own sentence, you do not need any introductory punctuation:
Evelyn described her father as a "stubborn old man."
You must also be careful about the placement of other punctuation marks at the end of quotations. Commas and periods always go inside quotation marks:
Lou said, "This class is way too noisy."
"This class is way too noisy," said Lou.
Question marks and exclamation points go inside the quotation marks if they are part of the original quotation:
The security guard asked, "Whose car is this?"
but remain outside the quotation marks if they are part of your own sentence:
Did the nurse say, "Dr. Adler will be coming soon"?
(In this case, the nurse is not asking the question; the writer of the sentence is.)
Semicolons and colons at the end of a quotation should be placed outside the quotation marks:
A certain novel begins with the words, "Call me Ishmael": do you know which novel it is?
The two main functions of the apostrophe are to form the possessive case of nouns (indicating ownership) and to indicate a missing letter or letters in a contraction.
When forming the possessive of a singular subject, 's is generally needed:
The student's locker was filled with textbooks.
Margie's bagels are delicious.
If a singular noun ends in s, you should still use 's to form the possessive:
Luis's car is parked on Main Street.
Her boss's office is very large.
However, some writers use an apostrophe alone when the noun is long and contains multiple s sounds. This is not incorrect:
Officer Gonzales' gun was stolen.
When forming the possessive of plural nouns, you should add only an apostrophe if the noun ends in s:
The students' grades were posted on the board.
But the occasional plural nouns that don't end in s need 's to form the possessive:
The children's center opens at 9 a.m.
In two unusual cases, 's is used to form a plural noun. This occurs when you want the plural form of a single letter or of a word referred to as the word itself, as in the following examples:
Patrick got straight A's throughout four years of college.
This brief contains too many whether's.
Never use an apostrophe to form the plural of a proper name:
The Blochs came over for dinner.
The apostrophe is also used to replace missing letters in a contraction. For example, in the following sentence:
The clerk said the office wouldn't be open on Saturday.
"wouldn't" is a contraction for "would not" -- the apostrophe replaces the missing o. Similarly, in the sentence
We're tired from studying too much.
"we're" stands for "we are," so the apostrophe replaces the missing a.
The two instances that cause the most confusion -- and the most mistakes -- in apostrophe usage are your/you're and its/it's.
Remember the contraction rule, and your choice should be clear. "You're" stands for "you are," while "your" is the possessive form of "you":
"You're the top student in your class," said the dean.
Likewise, "it's" stands for "it is" or "it has," while "its" is the possessive form of "it":
It's time for the orchestra to begin its rehearsal.
If you are confused about which word to use in a sentence, pause and ask yourself which meaning you want -- a contraction or a possessive noun.
A semicolon can be used to connect two independent clauses that are closely linked in meaning:
The professor began class at exactly 10 o'clock; students who arrived late missed some of the lecture.
In this example, the two clauses could stand alone as separate sentences, but joining them with a semicolon stresses the relationship between them. Using a comma alone to connect these clauses would not be sufficient and would create a run-on sentence.
A semicolon would also be used to connect independent clauses when a transitional word or phrase is used, such as:
The small airplane had a smooth flight; however, a sudden gust of wind made its landing a little rough.
Commas have a variety of functions within a sentence -- they may set off an introductory or appositive phrase, link independent clauses, or separate words listed in a series, among other uses. For a detailed discussion of the rules of comma usage, along with practice exercises, see the Purdue OWL section on commas.
One frequent question on comma usage concerns the serial comma. When three or more words, names, or phrases are listed together in a sentence, commas are needed to separate them. For example:
The graduate student admitted she had not read the works of Melville, Thoreau, or Steinbeck.
Silvia must go to a meeting, return some library books, and check on her lab assistants before heading home.
Note the commas before the words or and and in these sentences.
Punctuation with Citations
Citations are governed by a number of rules that are beyond the scope of this discussion. For guidance in proper citation format, you should consult the Bluebook; also helpful are the Cornell and Lexis-Nexis sites devoted to citation style.
However, here are a few basic rules regarding punctuation placement with citations. A citation that appears after a complete sentence should be treated as a complete sentence itself, beginning with a capital letter and ending with a period. This holds true whether the citation is a long or short form. If a cite is given in the middle of a sentence, it must be set off by commas. Notice the punctuation of the citations in the following example:
In New York, the rule is well settled that an advertisement is merely an invitation to enter into negotiations, and is not an offer that may be turned into a contract by a person who communicates an intention to purchase the advertised item. Geismar v. Abraham & Strauss, 439 N.Y.S.2d 1005 (Dist. Ct. Suffolk Co. 1981); Lovett v. Frederick Loeser & Co., 207 N.Y.S.753 (Manhattan Mun. Ct. 1924). The only general test is the inquiry whether the facts show that some performance was promised in positive terms in return for something requested. Lovett, 207 N.Y.S.2d at 755. However, a purchaser may not make a valid contract by mere acceptance of a "proposition," Schenectady Stove Co., 101 N.Y. at 48, nor does the purchaser have the right to select an item which the seller does not have in stock or is not willing to sell at a reduced price. Lovett, 207 N.Y.S. at 757.
As illustrated in the first citation, when two or more cases are named, they must be separated by a semicolon. Also, be careful not to italicize the comma following the name of the case.
The following paragraph contains eight punctuation errors; see if you can find and correct them all.
Courts in New York treat a general advertisement as an invitation to all persons to enter into negotiations rather than an offer which, upon acceptance, may be turned into a contract. In Schenectady Stove Co., for example; the plaintiff delivered to defendant a catalogue of prices containing a statement of terms for sale, but the catalogue didnt state the amount of goods which plaintiff was willing to sell on those terms. Under these circumstances, the Court of Appeals held that no contract was ever made between the parties' with respect to an order that defendant submitted because the plaintiff had not made an offer that was complete and definite in all material terms. Hence, it was not possible for the defendant to make a valid contract by mere acceptance of a "proposition". 101 N.Y. at 48 Similarly, in Lovett, a department store advertised that it would sell, deliver and install certain "wellknown standard makes of radio receivers at 25 per cent. to 50 per cent. reduction' from advertised list prices...The court held that a department stores advertisement was not an offer but an invitation to all persons that the advertiser was ready to receive offers for the goods upon stated terms. 207 N.Y.S. at 755-756.