Which sentence uses a hyphen in a compound modifier correctly?

• A. She is a well-known author.
• B. She is a well known author.
• C. She is a well-known writer.
• D. She is a well-known authorhyphen.

Answer: (A)

When a compound modifier precedes a noun, you join its parts with a hyphen so they read as one idea describing the noun. Here, well-known describes the author as a single combined attribute, and it comes directly before the noun, so a hyphen is required. That makes the phrase a single descriptive unit: well-known author. Without the hyphen, well known author can look like two separate adjectives describing the noun, which is not the standard formal usage. The last option isn’t a proper sentence at all. The same rule would apply if the noun were writer: well-known writer.