Compound words may be written as unbroken words, hyphenated words or separate words. The unbroken, unhyphenated form is generally preferred, but hyphens should be used in the follow­ing cases:

• when the word to which the prefix is added is a proper name.

non-British

• when the prefix is added to a hyphenated word.

non-fear-conditioning trials

However, when such complicated phrases appear, it is sometimes better to recast the sentence in another form.

• when the compound is formed with self

self-explanatory

Words with the following prefixes do not require a hyphen: anti-, bi-, co-, de-, infra-, mid-, non-, over-, pre-, post-, re-, semi-, sub-, up-, and un-.

Hyphens are also used in compound words functioning as adjectives. A compound modi­fier that is placed before the noun it modifies is usually hyphenated to avoid ambiguity.

Initial information-processing strategies became important.

But: Initial strategies for information processing became im­po­rt­ant.