Hayley教口语，“一成不变”用英语怎么说？

If an agreement, policy, or rule is set in stone, it is completely decided and cannot be changed.

如果一项协议、政策或规则是set in stone(固定不变的)，意思是它已经完全决定了，不能改变。

The relationship between popcorn and the movies was really set in stone during World War II.

在二战期间，爆米花和电影之间的关系一度如同板上钉钉般坚定。

not be set in stone

to be able to be changed

还未确定;未成定局

These are just a few ideas - nothing is set in stone yet.

这还只是一些想法——什么都还没定下来。