irreplaceable 不能调换的，不能代替的
So you might say that the ring is irreplaceable.
所以那只戒指可说是无可取代
She said that india had lost an irreplaceable part of its heritage.
她说印度丢失了一项不可替代的遗产。

for generations 几代相传; 祖祖辈辈
For generations they have defined their leaders through political jokes.
几代人以来他们都用政治漫画描画他们的领袖。
This recession is going to reshape america for generations, including the way we live and work.
这次经济衰退将重新塑造几代美国人，包括我们的生活和工作方式。