milestone
/ˈmaɪlstəʊn/noun
1- a stone set up beside a road to mark the distance in miles to a particular place里程碑。
1.1
- figurative an event marking a significant change or stage in the development of something〈喻〉里程碑式事件, 里程碑：
the speech is being hailed as a milestone in race relations.
这次演讲被赞为种族关系的里程碑。