Punctuation
Ampersands
Only use ampersands when space is an issue or for company names, abbreviations and common expressions (e.g. R&D). Otherwise write and.
Apostrophes
Use apostrophes to indicate a missing letter in a contraction and to form possessive nouns.
For all singular possessive nouns, add an apostrophe and an s, even if the noun ends in an s.
For plural possessive nouns that end in an s, just add the apostrophe.
Colons
Use colons to introduce lists or concepts.
If you use a colon to join related sentences, you don’t need to capitalize the first word in the second sentence.
Don't use them in UI labels such as buttons or fields.
Commas
If required, use the Oxford comma to clarify sentences in which things are listed. Don't use the Oxford comma if the sentence is clear without it.
Avoid complex sentences that require lots of commas.
When writing the abbreviation of for example, use the British English spelling without the comma.
Ellipses
Use ellipses in labels or messages to indicate that something is in progress, or that information is incomplete or truncated.
Don’t use them in search box placeholders.
Remove the space before the ellipsis. If there’s a new sentence after, include a space.
Use a midline ellipsis without spaces to redact sensitive information.
Em dashes
Use two em dashes to set off a phrase in the middle of a sentence.
Use one em dash to set off a phrase or clause at the end of a sentence.
Don't include spaces.
Exclamation points
Use single exclamation points sparingly.
You can choose to use them in greetings, congratulatory messages and when you want to generate some excitement (e.g. a new feature announcement).
Don’t use them in error messages or alerts. Don't use more than a single exclamation point.
Hyphens
Use hyphens to create hyphenated compound words.
When 2 or more compound modifiers have a common base, omit the base in all except the last modifier, but retain the hyphens.
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In general, don't include a hyphen after the following prefixes unless it's necessary to avoid confusion or if the word following the prefix is capitalized:
auto-, bi-, co-, cyber-, exa-, giga-, kilo-, mega-, micro-, multi-, non-, pre-, re-, sub-, tera-, un-.
Parentheses
Use parentheses to define acronyms and to define additional information at the end of a sentence.
Only capitalize content in parentheses if it’s an acronym, a proper noun or part of an element that’s always capitalized (e.g. a field label).
Avoid placing plurals in parentheses, unless it’s vital to specify that the number can be singular or plural. This is because they add to the user’s cognitive load and can be difficult to localize.
Instead, ask Engineering to implement two different versions. If this isn’t possible, use the plural.
Periods
Use periods for complete sentences.
Don’t use periods for short sentences (3 words or fewer), UI labels (titles, buttons, fields, standalone links etc) and lists.
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For more info, see Writing for UI elements.
Question marks
Use questions marks sparingly. If you're asking the user a question, include a question mark.
Quotation marks
Use double curly quotation marks for direct quotations. Straight quotation marks should only be used in code.
If the quoted speech includes an additional quote, the latter should be in single quotes.
When telling the user to enter something exactly in a field, use curly double quotes.
If you need to highlight characters in validation or error messages, use curly single quotes.
Semicolons
Avoid using semicolons. Lots of readers don’t understand their purpose and they can result in complex sentences. Instead, break the text down into shorter sentences.
Slashes
Use slashes for URLs and to imply a combination. Use backslashes for servers and folders.
Capitalize the word after the slash if the word before the slash is capitalized.
Don’t include spaces.