When should you use a hyphen in a compound word?

A hyphen should be used in a compound word in the following situations:

1. When two or more words are combined to form a single adjective before a noun. For example, "well-known author" or "high-quality product."

2. When a compound word is used as a modifier and comes before a noun. For example, "state-of-the-art technology" or "time-saving technique."

3. When a compound word is used to avoid confusion or to clarify meaning. For example, "re-cover" (to cover again) versus "recover" (to regain health).

4. When a prefix is added to a proper noun or a capitalized word. For example, "pre-World War II" or "anti-American sentiment."

5. When a compound word is used as a noun or a verb and is not commonly recognized as a single word. For example, "mother-in-law" or "check-in."

It is important to note that not all compound words require a hyphen. Many compound words have become widely accepted as a single word over time, and in such cases, a hyphen is not necessary. It is always recommended to consult a dictionary or style guide for specific compound word usage.