It literally says [b]teen[/b]ager. Why is this a question? It lasts from the moment you enter your teens, AKA when you turn 10, until you turn 20, and are thus out of your teens and into your twenties. What you guys are talking about is [i]adolescence[/i], which starts at puberty (12-13) and ends at 18 (when you enter adulthood).