Adult
From the Simple English Wikipedia, the free encyclopedia that anyone can change
An adult is someone grown up completely. It is the phase after being teenagers.
In many countries someone is an adult when he/she is older than 18 years.
But there are exceptions like Japan or South Korea which do not see a human as an adult until he/she 19 or 20 years old.
There are also some cultures that say a person is an adult from an age of 12 years on.

