21.2.3 Nonrestrictive Clauses and Phrases
21.12 Multiple Punctuation Marks
This chapter offers general guidelines for punctuation in the text of your paper. Some rules are clear-cut, but others are not, so you often have to depend on sound judgment and a good ear.
Special elements such as abbreviations, quotations, and source citations have their own guidelines for punctuation, which are treated in relevant chapters in this book.
If you are writing a thesis or dissertation, your department or university may have specific requirements for punctuation, which are usually available from the office of theses and dissertations. If you are writing a class paper, your instructor may also ask you to follow certain principles for punctuation. Review these requirements before you prepare your paper. They take precedence over the guidelines suggested here. For style guides in various disciplines, see the bibliography.
A period ends a sentence that is a declarative statement, an imperative statement, or an indirect question. A period can also end a sentence fragment, if the context makes its rhetorical function clear, but this usage is rare in academic writing. In all these cases, the period is a terminal period and, between sentences, should be followed by a single space.
Consider the advantages of this method.
The question was whether these differences could be reconciled.
Put a period at the end of items in a vertical list only if the items are complete sentences (see 23.4.2). Otherwise, omit terminal periods, even for the last item, and do not capitalize the first words.
The report covers three areas:
1. the securities markets
2. the securities industry
3. the securities industry in the economy
Individual periods can also be used in other contexts, including abbreviations (see especially 24.1.3) and citations (16.1.2 and 18.1.2), and also in URLs (20.4.2, 17.1.7, and 19.1.8), where they are often called dots. Strings of periods, or dots, can be used in quotations (see 25.3.2), where they are called ellipses, and in tables (26.2.6) and front matter pages (A.2.1), where they are called leaders.
Do not use periods after chapter and part titles and most subheadings (see A.2.2) or after table titles (26.2.2). For periods in figure captions, see 26.3.2.
Commas separate items within a sentence, including clauses, phrases, and individual words. They are especially important when a reader might mistake where a clause or phrase ends and another begins:
Before leaving the members of the committee met in the assembly room.
Before leaving, the members of the committee met in the assembly room.
For use of commas in numbers, see 23.2.2. For use of commas in citations, see 16.1.2 and 18.1.2.
In a sentence containing two or more independent clauses joined by a coordinating conjunction (and, but, or, nor, for, so, yet), put a comma before the conjunction. This is not a hard-and-fast rule; no comma is needed between two short independent clauses with no internal punctuation.
Students around the world want to learn English, and many young Americans are eager to teach them.
The senator arrived at noon and the president left at one.
In a sentence containing three or more short and simple independent clauses with no internal punctuation, separate the clauses with commas and add a coordinating conjunction before the last one. (Always include a comma before the coordinating conjunction.) If the clauses are longer and more complex, separate them with semicolons (see 21.3)—or, better, rewrite the sentence.
The committee designed the questionnaire, the field workers collected responses, and the statistician analyzed the results.
The committee designed the questionnaire, which was short; the field workers, who did not participate, collected responses; and the statistician analyzed the results, though not until several days later.
Ordinarily, do not insert a comma before a conjunction joining two subjects or two predicates.
The agencies that design the surveys and the analysts who evaluate the results should work together.
They do not condone such practices but attempt to refute them theoretically.
When a sentence with two independent coordinate clauses opens with a phrase or dependent clause that modifies both, put a comma after the introductory element but not between the two independent clauses.
Within ten years, interest rates surged and the housing market declined.
In a series consisting of three or more words, phrases, or clauses with no internal punctuation of their own, separate the elements with commas. Always use a comma before the conjunction that introduces the last item.
The governor wrote his senators, the president, and the vice president.
Attending the conference were Fernandez, Sullivan, and Kendrick.
The public approved, the committee agreed, but the measure failed.
Do not use commas when all the elements in a series are joined by conjunctions.
The palette consisted of blue and green and orange.
If a series of three or more words, phrases, or clauses ends with an expression indicating continuation (and so forth, and so on, and the like, or etc.), punctuate that final expression as though it were the final item in the series. You may, however, add a comma after the continuation expression to prevent confusion after a long series.
They discussed movies, books, plays, and the like until late in the night.
Using such techniques, management can improve not only productivity but also hours, working conditions, training, benefits, and so on, without reducing wages.
Use semicolons to separate the items in a series if one or more includes commas, or if the items are long and complex (see 21.3). If such a series comes before the main verb of a sentence, however, rephrase the sentence.
The three cities that we compare are Hartford, Connecticut; Kalamazoo, Michigan; and Pasadena, California.
but not
Hartford, Connecticut; Kalamazoo, Michigan; and Pasadena, California, are the three cities that we compare.
Use paired commas to set off a nonrestrictive clause. A clause is nonrestrictive if it is not necessary to uniquely identify the noun it modifies.
These five books, which are on reserve in the library, are required reading.
Here, the noun phrase These five books uniquely identifies the books that the writer has in mind; the nonrestrictive clause is not necessary to identify the books further. On the other hand, in the following sentence, the dependent clause (that are required reading) is restrictive, because it identifies a specific subset of books that are on reserve at the library. Commas are therefore not used around the clause.
The books that are required reading are on reserve in the library.
Although which is often used with restrictive clauses, American writers generally preserve the distinction between restrictive that (no comma) and nonrestrictive which (comma).
The principles described above apply also to restrictive and nonrestrictive phrases.
The president, wearing a red dress, attended the conference.
The woman wearing a red dress is the president.
Commas are used in a variety of other situations. (For commas in dates, see 23.3.1.)
■ Introductory words and phrases. When you begin a sentence with an introductory element of more than a few words, follow it with a comma. A comma is not necessary after a short prepositional phrase unless the sentence could be misread without one.
If the insurrection is to succeed, the army and police must stand side by side.
Having accomplished her mission, she returned to headquarters.
To Anthony, Blake remained an enigma.
After this week the commission will be able to write its report.
■ Two or more adjectives preceding a noun. Separate two or more adjectives preceding a noun with commas when they could, without affecting meaning, be joined by and. Do not use a comma if one or more of the adjectives is essential to (i.e., forms a unit with) the noun. (Test: if you cannot change the order of the adjectives, do not use commas.)
It was a large, well-placed, beautiful house.
They strolled out into the warm, luminous night.
She refused to be identified with a traditional political label.
■ Clarifying comments. Words and phrases such as namely, that is, and for example, which usually introduce a clarifying comment, should be followed by a comma but preceded by something stronger (such as a semicolon or a period). When you use or in the sense of “in other words,” put a comma before it. (These and similar expressions may also be set off by dashes or parentheses; see 21.7.2 and 21.8.1.)
Many people resent accidents of fate; that is, they look on illness or bereavement as undeserved.
The compass stand, or binnacle, must be visible to the helmsman.
■ Appositives. A word or phrase is said to be in apposition to a noun when it follows the noun and provides an explanatory equivalent for it. Non-restrictive appositives are set off by commas; restrictive appositives are not (see 21.2.3).
Chua, a Harvard College graduate, taught at Duke for several years.
Kierkegaard, the Danish philosopher, asked, “What is anxiety?”
but
The Danish philosopher Kierkegaard asked, “What is anxiety?”
■ Place-names. Use commas to set off multiple individual elements in names of places. (For commas in addresses, see 23.1.7.)
Cincinnati, Ohio, is on the Ohio River.
The next leg of the trip was to Florence, Italy.
■ Interjections and conjunctive adverbs. Set off interjections, conjunctive adverbs, and the like to suggest a break in the flow of thought or the rhythm of the sentence. But omit commas when such elements do not break the continuity of the sentence.
Nevertheless, it is a matter of great importance.
It is, perhaps, the best that could be expected.
Perhaps it is therefore clear that no deposits were made.
■ Contrasted elements. Put commas around an interjected phrase beginning with not, not only, or similar expressions. But when such a phrase consists of two components (not … but, not only … but also, and the like), commas are usually unnecessary. Use a comma between clauses of the more … the more type unless they are very short.
The idea, not its expression, is significant.
She was delighted with, but also disturbed by, her new freedom.
He was not only the team’s president but also a charter member.
The more it stays the same, the less it changes.
The more the merrier.
■ Parenthetical elements. Use paired commas when you set off a parenthetical element between a subject and a verb or a verb and its object. If you find yourself setting off more than one such interrupting element in a sentence, consider rewriting the sentence.
The Quinn Report was, to say the least, a bombshell.
Wolinski, after receiving instructions, left for Algiers.
■ Repeated words. Use a comma to separate identical words. An exception is normally made for the word that.
They marched in, in twos.
Whatever is, is right.
but
She implied that that did not matter.
A semicolon is stronger than a comma and marks a greater break in the continuity of a sentence. Use a semicolon in a compound sentence to separate independent clauses that are not connected by a coordinating conjunction (and, but, or, nor, yet, for, so).
One hundred communities are in various stages of completion; more are on the drawing board.
You can also use a semicolon with a coordinating conjunction if the clauses are long and have commas or other punctuation within them. But if the result seems unwieldy, consider replacing the semicolon with a period.
Although productivity per capita in the United States is much higher than it is in China, China has an increasingly well educated young labor force; but the crucial point is that knowledge—which is transferable between peoples—has become the most important world economic resource.
Use a semicolon before the words then, however, thus, hence, indeed, accordingly, besides, and therefore when those words are used transitionally between two independent clauses.
Some think freedom always comes with democracy; however, many voters in many countries have voted for governments that they know will restrict their rights.
When items in a series have internal punctuation, separate them with semicolons (see also 21.2.2).
Green indicates vegetation that remained stable; red, vegetation that disappeared; yellow, new vegetation.
Semicolons are also sometimes used in titles (see 17.1.2 and 19.1.3) and to separate citations to more than one source (see 16.3.5.1 and 18.3.2.5).
A colon introduces a clause, phrase, or series of elements that expands, clarifies, or exemplifies the meaning of what precedes it. Between independent clauses, it functions much like a semicolon, though more strongly emphasizing balance or consequence.
People expect three things of government: peace, prosperity, and respect for civil rights.
Chinese culture is unrivaled in its depth and antiquity: it is unmatched in its rich artistic and philosophical records.
Use a colon to introduce illustrative material or a list. A colon should follow only a complete independent clause; often an introductory element such as the following or as follows should precede the colon. (See also 23.4.2.)
The qualifications are as follows: a doctorate in economics and an ability to communicate statistical data to a lay audience.
but not
The qualifications are: a doctorate in economics …
Note that the first word following a colon within a sentence is generally not capitalized unless it is a proper noun or unless the colon introduces more than one sentence. For capitalization in quotations introduced by a colon, see chapter 25.
Colons are also used in titles (see 17.1.2 and 19.1.3), in notations of time (23.1.5), in URLs (17.1.7 and 19.1.8), and in various ways in citations.
Put a question mark at the end of a complete sentence phrased as a question.
Who would lead the nation in its hour of need?
Put a question mark after a clause phrased as a question and included as part of a sentence. Do not use quotation marks unless the question is a quotation and the rest of the sentence is not.
Would the union agree? was the critical question.
If the included question is at the end of the sentence, do not add a period after the question mark. You are not required to capitalize the first word of the included question, but an initial capital helps readers identify the question, especially if it includes internal punctuation. If the sentence becomes awkward, you may instead rephrase the question as a declarative statement.
Several legislators raised the question, Can the fund be used in an emergency, or must it remain dedicated to its original purpose?
Several legislators raised the question of using the fund in an emergency, which was not its original purpose.
A question mark may also indicate doubt or uncertainty, as in a date.
The painter Niccolò dell’Abbate (1512?–71) assisted in the decorations at Fontainebleau.
Exclamation points are rarely appropriate for academic writing, except when they are part of quoted material or part of the title of a work (the musical Oklahoma!). See also 21.12.2.1.
Hyphens are used in a variety of contexts, including compound words (see 20.3) and inclusive numbers (23.2.4).
A dash is an elongated hyphen used to set off text in a way similar to but more prominent than commas (see 21.2) or parentheses (21.8.1). Also called an em dash (because in most fonts it is approximately the width of the capital letter M), this character is available in most word processors.1 It can be represented with two consecutive hyphens, but most word processors can be set to convert double hyphens to em dashes automatically. Do not leave space on either side of the dash.
When you use dashes to set off a parenthetical element, pair them as you would commas or parentheses. But avoid using more than one pair in any one sentence; instead, use parentheses for the second layer of parenthetical information.
The influence of three impressionists—Monet (1840–1926), Sisley (1839–99), and Degas (1834–1917)—is obvious in her work.
You can also use a single dash to set off an amplifying or explanatory element.
It was a revival of a most potent image—the revolutionary idea.
Use a dash or a pair of dashes enclosing a phrase to indicate a strong break in thought that also disrupts the sentence structure.
Rutherford—how could he have misinterpreted the evidence?
Some characters in Tom Jones are “flat”—if you do not object to this borrowing of E. M. Forster’s somewhat discredited term—because they are caricatures of their names.
A dash may also introduce a summarizing subject after a list of several elements.
The statue of the discus thrower, the charioteer at Delphi, the poetry of Pindar—all represent the great ideal.
When you quote from a mutilated or illegible text, indicate a missing word or missing letters with a 2-em dash (formed with two consecutive em dashes, or four hyphens). For a missing word, leave a space on either side of the dash; for missing letters, leave no space between the dash and the existing part of the word.
The vessel left the ____ of July.
H____h? [Hirsch?]
The same technique can be used when you want to obscure a particular word.
It was a d____ shame.
A 3-em dash (formed with three consecutive em dashes, or six hyphens) is used in bibliographies and reference lists to represent the repeated name of an author or editor (see 16.2.2 and 18.2.1).
Parentheses usually set off explanatory or interrupting elements of a sentence, much like paired commas (see 21.2) and dashes (21.7.2). In general, use commas for material closely related to the main clause, dashes and parentheses for material less closely connected. The abbreviations e.g. and i.e., which may introduce a clarifying comment (see 24.7), are used only in parentheses or in notes.
The conference has (with some malice) divided into four groups.
Each painting depicts a public occasion; in each—a banquet, a parade, a coronation (though the person crowned is obscured)—crowds of people are pictured as swarming ants.
There are tax incentives for “clean cars” (e.g., gasoline-electric hybrids and vehicles powered by compressed natural gas and liquefied propane).
Parentheses can also be used with citations (see chapters 16 and 18) and to set off the numbers or letters in a list or an outline (see 23.4.2).
Brackets are most often used in quotations, to indicate changes made to a quoted passage (see 25.3 for examples). They can also be used to enclose a second layer of parenthetical material within parentheses.
He agrees with the idea that childhood has a history (first advanced by Philippe Ariès [1914-84] in his book Centuries of Childhood [1962]).
The forward slash (/) is used in a few contexts, such as fractions (see 23.1.3) and quotations of poetry (see 25.2.1.2). Single and double slashes appear in URLs and other electronic identifiers (see 20.4.2). The backward slash (or backslash, \) has various meanings in different computer languages and operating systems.
For the use of quotation marks in quoted material, see 25.2.1.2. For use in titles and other special situations, see 22.3.2. For use in citations, see 16.1.4 and 18.1.4.
Some fields—linguistics, philosophy, and theology, for example—use single quotation marks to set off words and concepts. The closing quotation mark should precede a comma or period in this case (compare 21.12.2).
kami ‘hair, beard’
The variables of quantification, ‘something’, ‘nothing’,…
In most other fields, follow the guidelines in 22.2.2 for using quotation marks and italics with definitions of terms.
For the use of apostrophes in plural and possessive forms, see 20.1 and 20.2. Apostrophes are also used in forming contractions (don’t). If your word processor is enabled to use directional or “smart” quotation marks, make sure not to confuse an apostrophe for a left single quotation mark (’twas, not ‘twas).
The guidelines given throughout this chapter sometimes call for the use of two punctuation marks together—for example, a period and a closing parenthesis. The guidelines below show when to omit one of the marks and the order of the marks when both are used.
Except for ellipses, never use two periods together, even when a period in an abbreviation ends a sentence. Keep the abbreviation period when a sentence ends with a question mark or an exclamation point.
The exchange occurred at 5:30 p.m.
Could anyone match the productivity of Rogers Inc.?
If a situation calls for both a comma and a stronger punctuation mark, such as a question mark or a dash, omit the comma.
“What were they thinking?” he wondered to himself.
While the senator couldn’t endorse the proposal—and he certainly had doubts about it—he didn’t condemn it.
An exception can be made for titles of works that end in a question mark or an exclamation point. Because such punctuation is not strictly related to the rest of the sentence, retain commas where needed.
“Are You a Doctor?,” the fifth story in Will You Please Be Quiet, Please?, treats modern love.
Films such as Airplane!, This Is Spinal Tap, and Austin Powers offer parodies of well-established genres.
Adjacent marks of punctuation most often occur with quotation marks, parentheses, or brackets. American usage follows a few reliable guidelines for ordering multiple marks.
21.12.2.1 WITH QUOTATION MARKS. A final comma or period nearly always precedes a closing quotation mark, whether it is part of the quoted matter or not.
In support of the effort “to bring justice to our people,” she joined the strike.
She made the argument in an article titled “On ‘Managing Public Debt.’”
There are two exceptions. When single quotation marks are used to set off special terms in certain fields, such as linguistics, philosophy, and theology (see 21.10), put a period or comma after the closing quotation mark.
Some contemporary theologians, who favored ‘religionless Christianity’, were proclaiming the ‘death of God’.
And if a computer file name or command must be put in quotation marks, a period or comma that is not part of the name or the command should come after the closing mark.
Click on Save As; name your file “appendix A, v. 10”.
Question marks and exclamation points precede a closing quotation mark if they are part of the quoted matter. They follow the quotation mark if they apply to the entire sentence in which the quotation appears.
Her poem is titled “What Did the Crow Know?”
Do we accept Jefferson’s concept of “a natural aristocracy”?
Semicolons and colons always follow quotation marks. If the quotation ends with a semicolon or a colon, change it to a period or a comma (or delete it) to fit the structure of the main sentence (see 25.3.1).
He claimed that “every choice reflects an attitude toward Everyman”; his speech then enlarged on the point in a telling way.
The Emergency Center is “almost its own city”: it has its own services and governance.
21.12.2.2 WITH PARENTHESES AND BRACKETS. When you enclose a complete sentence in parentheses, put the terminal period (or other terminal punctuation mark) for that sentence before the last parenthesis. However, put the period outside when material in parentheses, even a grammatically complete sentence, is included within another sentence. The same principles apply to material in brackets.
We have noted similar motifs in Japan. (They can also be found in Korean folktales.)
Use periods in all these situations (your readers will expect them).
Myths have been accepted as allegorically true (by the Stoics) and as priestly lies (by Enlightenment thinkers).
(The director promised completion “on time and under budget” [italics mine].)
For terminal punctuation with citations given parenthetically, see 25.2.
1. There is a second type of dash, called an en dash (because it is approximately the width of the capital letter N), that is used in published works to mean “through,” usually in connection with numbers or dates (e.g., 1998–2008). It can also be used in other contexts, as discussed in 6.78-81 of The Chicago Manual of Style, 16th edition (2010). If your local guidelines require it, this character is available in most word processors; otherwise use a hyphen in these contexts. Note that this book uses en dashes where they are appropriate, as in the preceding reference to CMOS.