Explain when a compound adjective should and should not be hyphenated.
Compound adjectives should be hyphenated when they are used before a noun to modify it. For example, in the phrase "a well-known author," "well-known" is a compound adjective that describes the noun "author." The hyphen is used to connect the two words and indicate that they function as a single unit modifying the noun.
Compound adjectives should not be hyphenated when they appear after the noun or when they are used as predicate adjectives. For example, in the sentence "The author is well known," there is no need to hyphenate "well known" because it is not directly modifying a noun. Similarly, in the phrase "The author is talented and well known," "well known" is used as a predicate adjective, and therefore no hyphen is needed.
It is also important to note that some common compound adjectives are always hyphenated regardless of their position in a sentence. For example, "five-year-old child" and "state-of-the-art technology" always have hyphens to maintain clarity and avoid confusion.