Punctuation provides vital clues for reader understanding. It’s governed by well-documented rules. For example, every English sentence requires end punctuation (unless it’s a title or a heading). Within those rules are stylistic choices, which we’ll cover here.
Writing tip The more punctuation you add, the more complex a sentence becomes. If a sentence contains more than a comma or two and ending punctuation, consider rewriting it to make it crisp and clear.
Learn more Refer to The Chicago Manual of Style to learn more about specific punctuation.
This section covers:
Don’t use end punctuation in headlines, headings, subheadings, UI titles, UI text, or simple lists (three or fewer words per item).
End all sentences with a period, even if they’re only two words. Put one space, not two, after a period.
Be brief—make every word count
Be brief. Make every word count.
When a phrase ending with a colon introduces a bulleted list:
- If one or more list elements complete the introductory phrase preceding the colon, use a period after every list element.
- If all list elements are short phrases (three words or fewer), don’t end them with periods, even if they form a complete sentence together with the list introduction.
- If one or more list elements are complete sentences, use a period after every element, even if a list element contains three or fewer words.
Use a comma
In a list of three or more items, include a comma before the conjunction. (The comma that comes before the conjunction is known as the Oxford or serial comma.)
- Outlook includes Mail, Calendar, People, and Tasks.
- Save your file to a hard drive, an external drive, or OneDrive.
Writing tip If a series contains more than three items or the items are long, consider a bulleted list to improve readability.
Following an introductory phrase.
- With the Skype app, you can call any phone.
- To join independent clauses with a conjunction, such as and, or, but, or so.
- Select Options, and then select Enable fast saves.
Writing tip If the sentence is long or complex, consider rewriting as two sentences.
Don’t use a comma
To join independent clauses when you don’t use a conjunction. (Use a semicolon instead.)
- Select Options; then select Enable fast saves.
- Between verbs in a compound predicate (when two verbs apply to a single subject).
- The program evaluates your computer system and then copies the essential files to the target location.
Writing tip Consider replacing a compound predicate with two sentences. Or add a subject for the second verb.
- The program evaluates your computer system. Then it copies the essential files to the target location.
- The program evaluates your computer system, and then it copies the essential files to the target location.
Use an apostrophe
To form the possessive case of nouns. For singular nouns, add an apostrophe and an s, even if the noun ends in s, x, or z. To form the possessive of plural nouns that end in s, add only an apostrophe.
- insider’s guide
- the box’s contents
- users’ passwords
- the Joneses’ computer
To indicate a missing letter in a contraction.
Don’t use an apostrophe
For the possessive form of it.
- Replace a formula with its calculated value.
With a possessive pronoun.
- The choice is yours.
To form the plural of a singular noun.
- Play your favorite games on all your devices.
Include a colon at the end of a phrase that directly introduces a list.
We can create a backup of all sorts of things to make the transition easier, including:
- The apps you’ve installed on your phone, along with high scores and progress from participating apps.
- The passwords for your accounts.
- Your call history.
Use colons sparingly at the end of a statement followed by a second statement that expands on it.
beqom doesn’t recognize this device for one of two reasons: the device wasn’t connected properly or the device isn’t a smartphone.
Most of the time, two sentences are more readable.
When you use a colon in a sentence, lowercase the word that follows it unless:
The colon introduces a direct quotation.
- What does it mean when I see a message that asks: “Are you trying to visit this site?”
The first word after the colon is a proper noun.
- We’re considering three cities for the event: Geneva, Munich, and London.
Sentences that contain semicolons are often complex. Try to simplify the sentence—break it into multiple sentences or a list—to eliminate the semicolon.
Between two independent clauses that aren’t joined by a conjunction.
- Select Options; then select Automatic backups.
Between contrasting statements that aren’t joined by a conjunction.
- What’s considered powerful changes over time; today’s advanced feature might be commonplace tomorrow.
Use questions sparingly. In general, customers want us to give them answers.
When a customer needs to make a decision, a question is appropriate.
In most content, use double quotation marks (“ ”) not single quotation marks (‘ ’).
In online content, use straight quotation marks.
Refer to quotation marks, opening quotation marks, and closing quotation marks. Don’t call them quote marks, quotes, open or close quotation marks, or beginning or ending quotation marks.
Place closing quotation marks:
- Outside commas and periods.
- Inside other punctuation.
Exception If punctuation is part of the quoted material, place it inside the quotation marks.
In compound words that precede and modify a noun as a unit, don’t hyphenate:
Very, when it precedes another modifier.
- Very fast test
An adverb ending in -ly, such as completely, when it precedes another modifier.
- extremely stylized image
- highly graphical interface
Note Use adverbs sparingly. They usually aren’t necessary.
Hyphenate two or more words that precede and modify a noun as a unit if:
Confusion might result without the hyphen.
- built-in drive
- high-level-language compiler
- read-only memory
- lower-left corner
- floating-point decimal
- line-by-line scrolling
- scrolling line by line
- up-to-date information
One of the words is a past or present participle (a verb form ending in -ed or -ing and used as an adjective or noun).
- left-aligned text
- free-flowing form
- well-defined schema
- The schema is well defined.
- The modifier is a number or single letter plus a noun or participle.
- two-sided arrow
- 5-point star
- y-coordinate values
Suspended compound modifiers
Don’t use suspended compound modifiers, such as left- and right-aligned text, unless space is limited. Instead, spell out the entire phrase.
- upper-right or lower-right corner
If you use a suspended compound modifier, include a hyphen with both adjectives. The first hyphen is followed by a space.
- upper- or lower-right corner
Don’t form suspended compound modifiers from one-word adjectives.
- uppercase and lowercase letters
Hyphenate compound nouns when one of the words is abbreviated.
Compound numerals and fractions
Hyphenate compound numerals and fractions.
a twenty-fifth anniversary
one-third of the page
In general, don’t include a hyphen after the following prefixes unless omitting the hyphen could confuse the reader.
Use a hyphen between a prefix and a stem word:
If a confusing word results without the hyphen.
Capitalize any part of a hyphenated compound word that would be capitalized if there were no hyphen. For example, capitalize the first word if it’s the first word of a sentence or heading.
Customer-friendly content is brief, accurate, and to the point.
Capitalize the final part of a hyphenated compound word if it’s the last word in a context that requires title capitalization, such as a book or song title.
Use an em dash (—) to set off a parenthetical phrase with more emphasis than parentheses provide. Don’t add spaces around an em dash.
Use one em dash on each side of a phrase embedded in a sentence.
- The information in your spreadsheet—numbers, formulas, and text—is stored in cells.
Use one em dash to set off a phrase at the end of a sentence.
- If you’re not sure about the details, look at the illustrations in the wizard—they can help you figure out what type of connection you’re using.
Don’t use an em dash:
- In place of a bullet character in a list.
- To indicate an empty cell in a table.
Don’t capitalize the first word after an em dash unless the word is a proper noun.
Use an en dash:
To indicate a range of numbers, such as inclusive values, dates, or pages.
For a minus sign.
- 12 – 3 = 9
To indicate negative numbers.
Don’t use an en dash to indicate an empty cell in a table.
Don’t use spaces on either side of an en dash.
Exception Surround an en dash with spaces when it’s used as a minus sign in an equation or in a time stamp appearing in UI.
12 – 3 = 9
2:15 PM 12/1/16 ‒ 4:45 PM 4/1/16.
In text, don’t use an en dash in a range of times. Use to instead: 10:00 AM to 2:00 PM. In a schedule or listing, use an en dash with no spaces around it: 10:00 AM–2:00 PM.
Exception In a date range that includes two times and two dates, add spaces around the en dash.
2:15 AM‒4:45 PM 4/1/16 (time range on a single day)
2:15 PM 12/1/17 ‒ 4:45 PM 4/1/18 (range includes both time and date)
Use exclamation points sparingly. Save them for when they count.