哪 (nǎ)
* "Which": It refers to a specific item or option from a limited group or set. It's used to ask for a selection from a known or previously mentioned group.
* Example: 你喜欢哪本书？ (Nǐ xǐhuan nǎ běn shū?) Which book do you like? (implies there are multiple books to choose from)
* "Where": It asks for the location of something.
* Example: 你家在哪儿？ (Nǐ jiā zài nǎr?) Where is your house?
什么 (shénme)
* "What": It asks for information about an unknown or unspecified thing. It's used when the options are unknown or limitless.
* Example: 你想吃什么？ (Nǐ xiǎng chī shénme?) What do you want to eat? (no specific food options are mentioned)
* "Why": When used with "为什么" (wèishénme), it asks for the reason or cause.
* Example: 你为什么不来？ (Nǐ wèishénme bù lái?) Why didn't you come?
Key Differences
* Specificity: 哪 implies a limited choice, while 什么 is for an open-ended question.
* Purpose: 哪 asks for selection from a known group, while 什么 seeks to discover unknown information.
Examples to illustrate
* 你想要哪件衣服？ (Nǐ xiǎng yào nǎ jiàn yīfu?) Which shirt do you want? (Implies you're looking at specific shirts)
* 你想要什么衣服？ (Nǐ xiǎng yào shénme yīfu?) What kind of shirt do you want? (Open-ended question, no specific options)
In Summary
* Use 哪 when asking for a choice from a known or limited group.
* Use 什么 when asking for information about something unknown or unspecified.
Remember, the correct usage of 哪 and 什么 depends on the context of your question.