2.3.2.2 Open, Hyphenated, and Closed Compound Words

When a compound form is not settled by the authorities listed in §1.4: Editorial Responsibilities, follow the general principles in CMS17. Established compounds often become closed over time, while temporary or less familiar compounds may remain open or hyphenated. Compound adjectives are often left open after the noun, but may need a hyphen before the noun when the meaning could otherwise be misread: a ritual-specific instruction, but the instruction is ritual specific.

Many prefixes normally form closed compounds, including anti-, co-, counter-, inter-, meta-, multi-, neo-, non-, post-, pre-, pseudo-, re-, semi-, sub-, and trans-. Use a hyphen, however, when the second element is a proper noun or proper adjective, when the closed form would be awkward, or when clarity requires it: pre-Thelemic, post-Crowleyan, non-Christian, anti-Masonic, neo-Gnostic. Some forms have become established as closed compounds and should be treated as single words: Neoplatonism, Neoplatonic, counterculture, subconscious. Forms with quasi- are usually hyphenated when adjectival and open when nominal: quasi-scientific (adj.), but quasi contract (noun).