1. As a noun meaning "immortal," "fairy," or "divine being":
* Xiān (仙) - pronounced with a rising tone (like "sheen")
2. As part of place names:
* Xiàn (县) - pronounced with a falling tone (like "shien")
It's important to know the context to determine the correct pronunciation.
For example:
* 仙女 (xiān nǚ): fairy
* 神仙 (shén xiān): god, immortal
* 县城 (xiàn chéng): county town
* 临安县 (lín ān xiàn): Lin'an County
If you're unsure, it's always best to ask a native speaker or use a Chinese pronunciation dictionary.