If 18/19 year olds are adults, why do some older adults (24-30 years old) call them babies? I remember being called a baby by these people when I was 18-19, even though I was an adult.

Because at 18-19 you are new to the adult world. You are the newborn adults. You still have so much to learn about being an adult. Most are just learning to do adult things like balancing a checkbook, or clothing and feeding themselves. In fact many don't even do that. They still rely on their parents for much of life's needs. By the time you are 24-30 you are working full time, paying your rent and utilities, an having to dal with all the realities of everyday adult life.

I've never heard anybody that age called a baby. I've often heard them called kids. Why? Because adulthood isn't about age, it's about maturity and the willingness to accept responsibility. While teens -- even late teens -- continue to act like kids they'll be treated that way.

And, no, I'm not being critical. It's the way humans grow up. I was a dreadful teen and it took me a few years really to hit my stride. You'll get there too.

If you're 18 and ship out in the Army or Marines? They won't call you baby anymore. You're an adult and a man regardless but doing some service time and no one will even think that again.