Function table?!

In 6 days I will have a kindergartener! Super excited and a tad bit sad at the same time.
So this morning in the car we were talking about backpack:

ME: Juju, we're going to get your new backpack this weekend.
JUJU: Oh yeah? Cool. It has to have function. you know, like pockets for my stuff.
ME: You mean it has to be functionable?
JUJU: FUNCTION TABLE?! You so silly. Functions are not tables. Functions are like pockets to put my new stuff. Like pencils, my water bottle.
ME: Pockets make your backpack functionable by having pockets that you can put stuff in.
JUJU: Well ok. *mutters quietly: a function table is not even real.*
ME: No Juju, its funk-tion-able (stressing each syllable)
JUJU: Ok, ok I get it. Backpacks have function. They called pockets.

I decided to not go all dictionary on him. Smart kid, got the basic concept. Whatev...I made "that" and I'm proud to send that to kindergarten (by THAT, I of course mean him).