sensible

• 小孩子还不懂事呢。

  The child isn't very grown-up yet.

• 你怎么这样不懂事？

  How can you be so thoughtless?

• 这样大的人还不懂事。

  How can you be so thoughtless at this age?

• 孩子大了，渐渐懂事了。

  As the boy grew older, he gradually became more prudent.

• 我爱这孩子懂事。

  I love that this child is so sensible.