1. teenager

Today we are going to learn “teenager”. It means someone who is between 13 and 19 years old.
(1) Like other teenagers at his age, the boy is a little rebellious.
(2) But, as a teenager, I had “better” things to do than hang out at the airport.

2. precocious

Another word is “precocious”. It means a child shows intelligence or skill at a very young age, or behaves in an adult way.
(1) That child is far too precocious.
(2) Terry was always doing something. He was like a precocious child, really.