Parents Talk: What Changes When a Child Turns 18?

There are many milestones of parenthood—but for me, today, three stand out: 

1. The day our first child was born. 
2. The day I noticed he'd grown taller than me. 
3. The day he became an adult. 

Number 1 took place 18 years ago this week. So Number 3 is very fresh. 

I couldn't put a finger on my feelings the day our oldest son turned 18. Was it a sense of accomplishment, love, pride, relief, maybe the mysteriousness of life? All I knew was I felt shaky and it wasn't from too much (or too little) caffeine. 

The night before, over a very late dinner (don't ask), I heard myself say, "Well, you have two and a half hours of childhood left."

That was weird. 

In the morning, the other two kids and I were sitting in the kitchen. Down the hall we heard a door open and a groggy voice grunt, "I'm an adult."

Now what? 

We now have something in the house called an "adult child." I had thought those were two different things. 

What changes when a child turns 18? He can vote. He can smoke. He can excuse his own absence at high school if he's sick. What about parental rules and family dynamics?

There are now three grownups and two kids, signaling a shift in our balance of power for the first time in more than a decade. That's probably good. But enforcing rules, like being home by midnight, could become more tricky. 

What do you think should change in a family when a child becomes an adult?