When should a hyphen be used in compound nouns?

A hyphen should be used in compound nouns in the following situations:

1. When two or more words are combined to form a single noun: In cases where two or more words are used together to create a new noun, a hyphen is used to connect them. For example, "mother-in-law," "well-being," or "self-confidence."

2. When a compound noun is used as an adjective: If a compound noun is used to modify another noun, a hyphen is used to connect them. For instance, "high-quality products," "state-of-the-art technology," or "time-saving techniques."

3. When a compound noun includes a number: If a compound noun includes a number, a hyphen is used to connect the words. For example, "two-thirds," "twenty-one," or "five-year plan."

4. When a compound noun includes a prefix or suffix: If a compound noun includes a prefix or suffix, a hyphen is used to connect the words. For instance, "pre-approval," "re-examine," or "anti-inflammatory."

5. When a compound noun is used to avoid confusion or ambiguity: If using a hyphen in a compound noun helps to clarify the meaning or avoid confusion, it should be used. For example, "re-cover" (to cover again) versus "recover" (to regain health).

It is important to note that not all compound nouns require a hyphen. Some compound nouns are written as one word (e.g., "football," "classroom"), while others are written as separate words (e.g., "ice cream," "cell phone"). The use of hyphens in compound nouns depends on the specific rules and conventions of the language.