How to say "which one?" in Chinese

哪 (nǎ) is a question word meaning "which," and 个 (gè) is a measure word for general objects. Together, 哪个 means "which one?"

Use 哪个 when you need to choose from a set of items. It's informal and works in most situations. For example, if someone offers you several dishes, you can ask 哪个? to clarify. Avoid using it for people; use 哪位 (nǎ wèi) for a more polite form.