milestone
🇺🇸
/ˈmaɪlstəʊn/
🇬🇧
/ˈmaɪlstəʊn/
A very important point in the growth or progress of something.
Learning to walk is a big milestone in a child's life.
A stone by the road that shows the distance to places.
The milestone showed we had 10 miles left to reach the town.