Une personne qui n'est pas encore marie est. ............

The term you are looking for to describe a person who is not yet married is **"célibataire."** In English, this translates to **"single."**

Let me clarify each option to further explain:

• Célibataire: This is the French word for someone who is not married and is equivalent to being single.
• Mari: This means "husband" in English, indicating a married man.
• Neveu: This translates to "nephew," which refers to the son of one's sibling, and has no direct relationship to marital status.
• Home: This appears to be a misspelling or error for "homme," which means "man" in French. It does not specify marital status.

Therefore, the answer to the question is **"célibataire,"** the term used to describe a person who is not yet married.