I think the problem is that we are trying to give a definition to a vague term. I'm legally an adult and have been for three years. I can drink legally (even though I choose not to), I can buy cigarettes legal (never exercised this right), and other rights that I haven't exercised and have no intention of ever excerising due to it goes against my beliefs (use your imagination for this one).

I'm techinally in the category of Young Adult/Earily Adulthood. In my mind a kid is means a some in middle childhood, at best earily teenage years. Of course, when I get to be about your age I'm sure I will probably consider someone 21 to be a kid.