Editorial Style Guide

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(Laurie Smith-Frailey)


Some general rules:

  1. Place one space after a period, not two (i.e., between sentences).

  2. Make the punctuation look the same as the word it goes with. If the last word of a sentence is set in italics, set the punctuation in italics.
    • Didn’t I recently see an article about “weird fields” in MIT Tech Talk?
  3. Don’t add additional periods if a sentence ends with an acronym. (Otherwise, do.)
    • She just received an M.B.A.
    • Was she excited about finally earning her B.A.?

Apostrophe and quotation mark

Smart quotes and apostrophes

In general, use smart quotes and apostrophes like these. Exception: Use straight quotes (only) in reference to measurement, e.g., feet and inches, or to degrees of longitude or latitude.

  • 4'6", not 4’6”

You can use the Tools AutoCorrect AutoFormat As You Type function in Microsoft Word for Mac to make this happen automatically. (Check “Replace as you type … ‘straight quotes’ with ‘smart quotes.’”) Shortcuts in Microsoft Word (for Macintosh users only):

For single quotes:

option (alt)+close bracket
and shift+ option (alt)+close bracket

For double quotes:

option (alt)+open bracket
and shift+ option (alt)+open bracket ’ ”

Class years

For class years or other abbreviations for years, make sure the apostrophe points toward what is missing.

  • Ray Stata is a member of the Class of ’57.
  • He went to high school in the ’40s.


To form the possessive, add an ’s to a singular term that does not end in an s. If the term is plural or ends in s, add only an apostrophe.


  • Mr. Jones’s


  • Martha’s Vineyard
  • Seven Years’ War

Do not use an apostrophe with an s (’s) where there is no possessive. This is a common problem with decades and numbers. The only exception comes when adding an s would result in a different word; use an apostrophe in these cases.

  • I am a child of the 1980s.
  • The temperature this weekend will be in the 90s.
  • The I’s on his report card stand for incomplete.
  • The dog could actually, painfully, catch its own tail.

Joint possessives

In the case of joint possession, i.e., when two or more people own something together, place the apostrophe or apostrophe s (‘s) only after the name closest to the item.


  • We’re going to Mom’s and Dad’s house for Thanksgiving.


  • We’re going to Mom and Dad’s house for Thanksgiving. (Mom and Dad jointly own one house.)
  • We’re going to Mom’s and Dad’s houses for Thanksgiving. (Mom and Dad each own at least one house.)

If this structure lends itself to misinterpretation, recast the sentence to avoid ambiguity.


  • Marion and Martha’s brother had green hair last week. (This is incorrect if Marion and Martha are not sisters.)


  • Martha’s brother and Marion both had green hair last week.

Double possessives.

See page 274 of The New York Public Library Writer’s Guide to Style and Usage for most of this discussion.

When you have a possessive meaning in an “of” phrase, add apostrophe s (‘s).


  • The puppy belongs to a friend of Jenny.


  • The puppy belongs to a friend of Jenny’s.


Contractions are shortened forms of words or phrases where an apostrophe replaces the omitted letter(s).

  • do not = don’t
  • was not = wasn’t

Omission of letters

Again, the apostrophe replaces the missing letter(s).

  • department = dep’t
  • rock ’n’ roll (Note that since two letters are omitted, two apostrophes are needed. Further, note that both apostrophes face in the direction of the missing letter.)

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Brackets are commonly used to set off the writer’s explanation within a quote, such as [sic] (which means intentionally so written, telling the reader that the writer is reproducing certain words exactly as they appeared or were said). Brackets can also be used when a word is inserted. Most other cases call for parentheses.

  • The girl said she “seed [sic] a rattlesnake.”
  • “I went to the [convenience] store, but I couldn’t find the salt.”


As introduction

The colon tells the reader to keep reading. It can precede a quotation, list, explanation or main clause. A colon should be preceded by a complete sentence. A colon should not be used after words like such as, between a verb and the rest of the sentence, or between a preposition and its object.

  • We will discuss three popular music styles today:jazz, blues, and rock and roll.
  • She had only one thing to say:“It’s over.”

In letters

Use a colon after a salutation in a formal business letter but a comma after the salutation in a personal letter.

  • Dear Mrs. Jones:
  • Dearest Jack,

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Comma used in dates and place names

The New York Public Library Writer’s Guide to Style and Usage calls the comma “one of the most misused and controversial marks of punctuation,” and covers its use in depth on pages 242 through 258. Although most of us were taught to insert commas wherever there would be a pause in speaking, the trend nowadays is toward “open” punctuation—i.e., minimizing the use of commas. To find out more about specific questions regarding the use of commas, please consult The New York Public Library Writer’s Guide.

This sub-section of the Guide will focus on two particular areas of comma usage that cause widespread confusion—dates and place names. Note that the topic of commas in a series (serial commas) is treated separately in the following sub-section.

Commas in dates

A comma should be placed before and after the year in a three-part date.

  • On January 22, 2004, Chuck Will from Proctor Academy spoke to the WebPub group about blogging.

When only the month and year are given, however, do not use commas.

  • Annmarie sent around the March 2004 ComDor staff meeting agenda.

Place names

When both a city and state (or country) are cited, a comma should be placed both before and after the state (or country) name, whether it’s abbreviated or not.

  • The Humor Conference has been held in Saratoga Springs, New York, every April for the past 20 years.
  • The cherry blossoms in Washington, D.C., are nationally renowned.

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Comma used in series (serial commas)

Always use serial commas.

  • Serial commas are the commas before the “and” or “or” concluding a list of three or more words, phrases, or clauses.
  • Four-year-old Madison’s favorite movies are Antz, Bugs, and Finding Nemo.
  • Hector’s favorite activities on his days off include fighting it out with his league mates at the ancient bowling alley on North Lyndon Street, shooting pike on the upper branch of the Lamoille River with his brother, and chowing down with his hunting buddies and their wives at Flo’s Diner in Morrisonville.

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Most communications use several types of dashes in addition to the hyphen. Two of the most commonly used are the em dash (the width of a capital M), and the en dash (the width of a capital N). Dashes should not be surrounded by spaces. Dashes are further addressed in The New York Public Library Writer’s Guide to Style and Usage beginning on page 263.See also hyphen.

Em dash

The em dash (—), the primary form of dash, is used to emphasize information that follows and/or to provide a stronger pause than a comma. Mac keystrokes:shift+option+hyphen.

For abrupt changes in the sentence.

  • Can she—will she—make the decision?
  • The reception—have you heard?—has been cancelled.

For amplifying, or for explanatory or digressive elements.
(Commas could also be used here.)

  • He had spent several hours on the plan—a plan that would put an end to his problems.

For setting off a defining element within a sentence.
(An em dash can also introduce in the same way a colon does.)

  • She only invited three men—those who could appreciate the movie—to go with her.
  • He wanted that doggy in the window—the one with the waggly tail.

En dash

The en dash(–) is longer than a hyphen but shorter than an em dash. Mac keystrokes:option+hyphen.

For inclusive dates and times.

Use in the same way that you would use the words through or to. Note: In more formal writing, including publications and Web pages, if “from,” “of” or a similar word precedes dates or times, DO NOT use an en dash; use to, through or and instead. See Date and Time Terminology—spans of time (or numbers).

  • The play will be performed at Kresge Auditorium September 1–13.
  • The dinner is 6:30–7:30 tonight. (not The dinner is from 6:30–7:30 tonight. Using from would necessitate a rewording to:The dinner is from 6:30 to 7:30 tonight.)
  • Similarly, you would write:The committee will meet from 3 to 5 p.m.

To hyphenate words that are already hyphenated.

  • a quasi-public–quasi-judicial body
  • the non-European–non-Asian population

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The ellipsis, a series of three dots (...), indicates that you have omitted part of a sentence. The part of the sentence that is omitted governs the number of periods, i.e., if you omit something mid-sentence, use three dots; if you omit something at the end of your sentence, use four dots (three for the ellipsis and one for the terminal period). These rules apply most often to quoted matter. See The New York Public Library Writer’s Guide to Style and Usage, pp. 308- 9.

Within a sentence

Use three periods with single spaces on either side of the trio.

  • I am leaving something … out of this sentence.

At the end of the sentence

Use three periods and terminal punctuation. (This usually translates to four periods.)

  • I am slicing off the end of this sentence….

Between sentences

Include terminal punctuation and add three periods.

This sentence is over but not complete.... And this sentence is picking up where the other left off.

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Exclamation point

The exclamation point is occasionally used at the end of a sentence to express surprise, enthusiasm, disbelief, or strong emotion. The operative word here is occasionally. Although the adage “You are allowed to use just three exclamation points in your lifetime” may be a bit austere, good writers use exclamation points in moderation.


  • John made his sales quota again, just as he has done every year for the past 28 years!
  • I really love peanut butter!


  • Congratulations on being awarded the Bronze Beaver!
  • “Good grief!” said Charlie Brown.
  • “I passed physics!” exclaimed the music major.

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Hyphens have many uses and are therefore often overused. They are used to show a connection, either between words or between syllables. Hyphens are used to form compound words in instances where not doing so would cause misunderstanding (See p. 407 for the chapter on Hyphenation and Compound Words; see also the Guide to Compounding, p. 417).

Another way to decide when a hyphen is needed is to consider how the words are used. Two words working together as an adjective modifier are hyphenated.

  • decision-making process
  • interest-bearing loan

If in doubt, consult a dictionary. For using hyphens in word division, refer to the general principles described on pp. 408-410. While most word processors do hyphenate automatically, a careful writer should proofread for proper word division anyway!

Compound modifiers

  • She is a first-year student.
  • He is concentrating on 19th- and 20th-century art.
  • That business is a wholly owned subsidiary of a state-of-the-art computer company.
    (Note: Words ending in ly are not hyphenated.)
  • Traffic in the Baltimore-Washington corridor will only grow in the next 10 years.

Don’t hyphenate titles and proper names unnecessarily.

  • Language Across the Curriculum

Also, don’t hyphenate compound proper nouns:

  • Asian American literature; Native American traditions

Phone numbers

Although many people use hyphens in phone numbers (617-258-5563), we do not. Note that area code parentheses are no longer used because many areas of the United States require callers to dial the area code for all calls, even local calls.

In ComDor, use periods instead of hyphens in phone numbers:617.258.5563 .

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Punctuation inside/outside closing quotation marks

Commas and periods are always placed inside closing quotation marks.

  • “We need more bananas,” Sally announced.
  • Tom replied, “I know. I ate the last banana yesterday.”

Semicolons and colons are placed outside.

  • Sally just announced, “We need more bananas”; however, don’t we need apples, too?

Question marks and exclamation marks are placed inside when the entire quotation is a question or exclamation; outside when only words or phrases are in quotation marks.

  • Did Harry just ask, “Don’t we need apples, too?”
  • Didn’t I just hear Sally say, “We need more bananas”?

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A semicolon is used to connect two independent clauses that could stand alone as two sentences but are closely related. It tells the reader, “Slow down; don’t stop.” Sometimes, a semicolon simply separates two parts of a sentence more distinctly than a comma.

The semicolon, unlike other forms of punctuation, goes outside of quotation marks and parentheses (pp. 258–261).

The most common uses for semicolons are:

Between main clauses—with or without a coordinating conjunction.

  • The party was a great success; and the revelries went on into the wee hours of the morning.
  • She went straight to bed; it was said she was never the same again.
  • The dinner was very sparse; the family had only bread and bacon.

Between main clauses with a conjunctive adverb (e.g., however, also, and besides).

  • She was an excellent student; however, she failed because she refused to attend class.

In a series containing internal commas.

  • He made her a wonderful breakfast of ham, eggs, and toast; did all the laundry; and even scrubbed the kitchen floor.
  • She is traveling to Cheyenne, Wyoming; Bismark, South Dakota; and Lansing, Michigan.

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Massachusetts Institute of Technology

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E-mail comdor-editguide@mit.edu