Hyphenating Compound Modifiers with Words Ending in -ly

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Wikipedia defines a compound modifier (also called a compound adjective, phrasal adjective, or adjectival phrase) as a compound of two or more attributive words: that is, two or more words that collectively modify a noun.

We frequently come across compound modifiers like “çevre dostu bina,” “kullanıcı dostu arayüz” and so on. What we should keep in mind is that we are not supposed to hyphenate these compounds formed by an adverb ending in ly plus an adjective.

Both the Associated Press Stylebook and the Chicago Manual of Style are clear on this.

The Chicago Manual of Style:

When compound modifiers (also called phrasal adjectives) such as open-mouthed or full-length precede a noun, hyphenation usually lends clarity. With the exception of proper nouns (such as United States) and compounds formed by an adverb ending in ly plus an adjective, it is never incorrect to hyphenate adjectival compounds before a noun. When such compounds follow the noun they modify, hyphenation is usually unnecessary, even for adjectival compounds that are hyphenated in Webster’s (such as well-read or ill-humored).

The Associated Press Stylebook:

When a compound modifier — two or more words that express a single concept — precedes a noun, use hyphens to link all the words in the compound except the adverb very and all adverbs that end in -ly: a first-quarter touchdown, a bluish-green dress, a full-time job, a well-known man, a better-qualified woman, a know-it-all attitude, a very good time, an easily remembered rule.

Incorrect: Environmentally-friendly buildings are also known as “green” buildings.

Correct:    Environmentally friendly buildings are also known as “green” buildings.

You can further read on how to hyphenate compound modifiers (grammar topic) here.