What makes someone an adult?

Financial independence? Not living in your parent's basement? Beating the final boss in Super Mario?

In the eyes of the law, you're an adult when you've reached 18. This is because the law assumes that upon reaching 18, you are mature enough to take responsibility for your actions. There are people who reach this state before 18, and there are those that reach it after 18. However, what is maturity and when is someone mature?

Maturity is based on self-awareness. Immature people know that they are immature and mature people know that they are mature. You can look on your actions and state whether they were mature or not; i.e., if your actions would be those taken by other mature people. I see maturity as the acceptance of general social norms. A mature person wants a job because every other mature person wants one too. A mature person doesn't want to live in their parent's basement because everybody else has their own apartment. And really, a mature person doesn't really care that much about video games; they don't fit into the "big picture."

I don't think that any of the three things I stated in the first paragraph and signs of being an adult. They may be something that you really want, but they don't make someone an "adult" because they say nothing about your character or how mature you are. With maturity comes adulthood.