milestone

毕业是人生重要的里程碑。

Graduation is an important ___milestone in life.

宝宝学会走路是成长过程中的一个重要里程碑。

Learning to walk is a major ___milestone in a baby's development.

出版第一本书是他写作生涯的重要里程碑。

Publishing his first book was a significant ___milestone in his writing career.