哪个 (nǎ gè) is a demonstrative pronoun meaning 'which one' and is used to ask for selection among two or more specific, countable items. It combines the interrogative 哪 (nǎ), meaning 'which', with the common measure word 个 (gè), which functions here as a generic classifier for people, objects, or concepts — similar to 'one' in English questions like 'Which one?'. Unlike 什么 (shénme, 'what'), 哪个 implies a limited, known set of options.

This word is frequently used in everyday spoken and written Chinese, especially when choosing from visible or previously mentioned items — for example, pointing to books on a shelf, selecting food at a restaurant, or identifying people in a group. It can stand alone as a subject or object, and often appears before a noun (e.g., 哪个苹果) when specifying the category. Tone is essential: nǎ (third tone) must not be mispronounced as nà (fourth tone, meaning 'that').