Hyphenate words only when needed for clarity.
Compound modifiers
Use hyphenated compound modifiers before a noun. A compound modifier acts as a single unit to modify the noun. When you use a compound modifier after a noun, don't hyphenate it.
Recommended: The app uses Android-specific techniques.
Recommended: The app uses techniques that are Android specific.
Adverbs ending in -ly
Don't hyphenate adverbs ending in -ly except where needed for clarity.
Recommended: Free, simple, and publicly available implementations
Not recommended: Free, simple, and publicly-available implementations
Recommended: To get profile information for the currently authorized user
Not recommended: To get profile information for the currently-authorized user
When to hyphenate
In general, don't hyphenate a word that has a prefix or suffix. However, we recommend hyphenating in the following scenarios:
- When the absence of a hyphen could cause confusion—for example, re-count, re-mark.
- When a hyphen clarifies the meaning or disambiguates from another word— for example, re-sign or resign.
- When the prefix ends in a vowel, and the word it precedes starts with the same vowel—for example, co-op, de-energize.
- When a number or a capital letter follows the prefix—for example, non-English, pre-1500, post-twelfth graders.
- When the prefix is self—for example, self-aware, self-important.
- When the prefix is followed by a word that is already hyphenated.
- When the prefix is followed by a compound word that contains a space. In this case, the space is replaced with a hyphen—for example, twentieth century but pre-twentieth-century music.
Compound words
Compound words are two or more words that are joined to form a new word. To determine whether to hyphenate a compound word, check the word list. If it's not in the word list, check a dictionary.
Range of numbers
Use a hyphen, not an en dash (–),
to indicate a range of numbers. If a hyphen introduces ambiguity, use words such as
from, to, and through for clarity. Don't mix hyphens with words.
For information about how to represent a range of numbers that includes units, see
Ranges of numbers with units.
Recommended: 8-20 files
Recommended: 5-10 minutes
Recommended: from 8 to 20 files
Not recommended: from 8-20 files
Spaces around hyphens
Never place a space on either side of a hyphen except when using a suspended hyphen, in which case you can leave a space after (but not before) the hyphen.
Suspended hyphens
When two or more compound modifiers have a common base, you can keep the hyphens but leave out the base for all except the last modifier. In the following examples, the base is hour.
Recommended: You can set up the system to scan for new files at one- or two-hour intervals.
Recommended: You can set up the system to scan for new files at one-, two-, or three-hour intervals.