Whether 是什么意思？哪些地方不能换成 if

Whether 用于讨论不同可能性之间的选择，常见于间接疑问：I don't know whether he'll come。Whether … or not 可以表示无论哪种情况，结果都一样：Whether you agree or not, the rules won't change。

know/ask/decide + whether + clause; whether + to + verb; preposition + whether + clause; Whether … or not, + clause

• Researchers are still debating whether social media makes teenagers less happy.
• Whether people live in cities or in the countryside, they need reliable internet access.
• Can you check whether the pharmacy is still open?

间接疑问中，if 和 whether 常可互换：I asked if the shop was open。但有些位置要用 whether：在 to + 动词前，如 whether to stay；在介词后，如 It depends on whether he agrees；以及句首表达让步的 whether … or not。作文中，whether 更正式，通常是稳妥的选择。