10 Punctuation

While much of our grammar remains the same across academic disciplines, different fields may have different requirements. Below, you will find excerpts from various OER and disciplinary style guides with information on when and how to use punctuation in your writing.

Commas

• Use a serial comma, i.e., a comma placed immediately before the coordinating conjunctive (and, or, nor) in a series of three or more terms.
  • Serial comma: There were cows, horses, and pigs in the barn.
  • No serial comma: There were cows, horses and pigs in the barn.
  • Do not use a serial comma when an ampersand (&) is used instead of the word and.
• Use commas in numerals over 999 (e.g., 1,000; 45,000)
• Use a comma after a long introductory phrase
• For dates, use a comma after the day when a date is presented in month-day-year style. Include a comma after the year if the date comes in the middle of a sentence.
  • Do not use a comma for dates presented in day-month-year style
  • Do not use a comma between a month and year and between a season and a year
• Use a comma after the words said, replied, asked, wrote, etc. to introduce a quotation

Semicolons and Colons

Semicolons

• Semicolons are commonly used in a sentence to link two or more independent clauses not joined by a conjunction.
• Semicolons with commas:
  • Use semicolons between items in a series when the items contain commas
  • Use semicolons between statistics that contain commas (APA)
• Use semicolons to separate items within parentheses, like multiple parenthetical citations, to avoid back-to-back parentheses. (APA)
• Semicolons are usually used before phrases like that is, for example, or namely. (Chicago)

Colons

• Colons are used to introduce a list, explanation, definition, example, etc.
• Lowercase what follows a colon unless it is a word normally capitalized or when the colon introduces a series composed of more than one sentence, a rule or principle, a question, a quotation, or dialogue.
• Use a colon in ratios and proportions (APA)
• Colons are usually used after phrases like as follows, the following, and other similar phrases. (Chicago)

Apostrophes

• Format for possessive nouns
  • add an apostrophe and an s after a singular noun
  • add only an apostrophe after a plural and singular noun that end in –s
  • add an apostrophe and an s after a plural noun that does not end in –s
  • add an apostrophe and an s to a singular proper noun
  • add only an apostrophe to a plural proper noun
• Use an apostrophe to form the plurals of letters used as letters (t’s)
  • Use an apostrophe to form the plurals of letter grades (A’s)
• Do not use an apostrophe to form the plural of an abbreviation or a number (PhDs or 1970s)

Quotation Marks

• Use the North American system for quotation marks: periods and commas always go inside quotation marks; semicolons and colons go outside.
• Use double quotes for all quoted matters. Single quotation marks should be reserved to enclose quotes within quotes. (e.g., Mark exclaimed, “You have driven a stake into my heart! Now I truly understand Caesar’s words, ‘Et tu Brute?’ How could you treat me so?”)
  • Some exceptions to this system may be appropriate in specific disciplines. Please check with your project manager or copy editor.
  • Quotation marks should appear in the same style as the surrounding text
• Use quotation marks to introduce the title of an article or book chapter
• For APA style, use double quotation marks to refer to a letter, word, phrase, or sentence as a linguistic example or as itself
  • For MLA and Chicago, use italics
• Use double quotation marks to reproduce material from a test item or verbatim instructions to participants (APA)

Slashes

• Use a slash between two nouns paired as opposites
• Use a slash to specify either of two possibilities (e.g. and/or)

Periods, Question Marks, and Exclamation Points

• Do not use periods in abbreviations, acronyms, and initialisms, except as noted in spelling list (e.g., et al., etc., i.e. are the most common that retain the periods).
• Use a period with initials in names
• Do not use periods in abbreviations of state, province, or territory names (e.g., IA)
• Do not use periods in abbreviations for academic degrees (e.g., MFA)
• Do not use periods in metric and nonmetric measurement abbreviations (e.g., cm)
• When a sentence inside parentheses stands alone by itself, put the period inside the closing parenthesis.
  • If only a portion of the sentence is inside parentheses, place the period outside of the parentheses (wherever you would place the period to end the sentence).
• Do not use a period in a chapter title or heading.
• If the punctuation is part of the quoted material, place a question mark and exclamation point inside quotation marks, parentheses, and brackets.

Hyphens, Dashes, and Parentheses

Hyphens

• Do not hyphenate Latin phrases used adjectivally: ad hoc proposal, post hoc analysis.
• For hanging hyphen constructions (15- to 19-year-olds), do not hyphenate after “to.”
• Use a hyphen in simple fractions (e.g., two-thirds).

Em dashes ( — )

• The em dash is the standard for breaking a sentence or setting off parenthetical statements.
• Do not use a space before or after an em dash
• In Pressbooks, the em dash is created by using two hyphens. In the Book view, two hyphens will look like one long (em) dash.
  • Microsoft Word will automatically create an em dash when you type two hyphens directly between two words with no spaces.
  • On Mac, pressing the Option key while pressing the hyphen key twice will create an em dash.
  • On Windows, the short Ctrl + Alt + minus sign (from the numeric keypad) will create an em dash.
• Em dashes can be placed after a question mark, an exclamation point, and a period when it is part of an abbreviation or followed by a quotation mark. Em dashes cannot be placed after a comma, colon, or semicolon.

En dashes (–)

• Use an en dash when expressing a range of numbers, such as a page range or a date range, e.g., 1955–2001.
• There should be no space on either side of the en dash.
• In Pressbooks, use one hyphen to indicate one short (en) dash.
  • Microsoft Word will automatically make an en dash when you type one hyphen with spaces before and after it (just remove the spaces after typing).
  • On Mac, pressing the Option key while pressing the hyphen key once will create an en dash.
  • On Windows, the shortcut Ctrl + minus sign (from the numeric keypad) will create an en dash.

Parentheses

• Do not use parentheses within parentheses. Use square brackets instead.
• Use parentheses to introduce an abbreviation in the text