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.


Not recommended: Free, simple, and publicly-available implementations

Recommended: Free, simple, and publicly available implementations

Not recommended: To get profile information for the currently-authorized user

Recommended: To get profile information for the currently authorized user

When to hyphenate

Don't hyphenate a word that has a prefix or suffix except in the following situations:

  • Where not doing so could cause confusion; for example, re-count, re-mark.
  • When a number or a capital letter follows the prefix; for example, non-English, pre-1500, post-twelfth graders.
  • When the prefix ends in a vowel, and the word it precedes starts with the same vowel; for example, co-op, de-energize.
  • 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 nonbreaking hyphen (‑), not an en dash (–), to indicate a range of numbers. For information about how to represent a range of numbers that includes units, see Ranges of numbers with units.


Not recommended: from 8–20 files (–)

Recommended: 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 example, the base is hour.


Recommended: You can set up the system to scan for new files at one-, two-, or three-hour intervals.