Is 20 still considered a child?

No, you are an adult

On your taxes, you are still considered a dependent. until your mid-20s (unless you're in grad school). But in general, it depends on how mature you are/act.

Maybe for tax purposes of they are in college. But emotionally, a young woman of 20 is no longer a child. However men seem to get older but many of them never grow up. They merely get called an adult around age 21.

No

No. But do people ever feel like they have become an adult? I know I don't.