善变的英文单词是 changeable，也可以翻译为 erratic或 fickle。这些词都可以用来描述某事物或人的性质不稳定、容易改变。例如：

1. She is quite changeable； she can easily change her mind.

2. His behavior is erratic, making it difficult to predict his actions.

3. He has a fickle nature and often changes his allegiances.

希望这些信息对你有所帮助!