What makes a meal a meal?

So I was wondering, what make a meal a meal? Is it the same for everyone? I mean, is there a structure to a meal that we all understand?

Personally I rarely eat dessert, at least not at home, yet I recognize that dessert is considered an expected part of a meal, at least at dinner. When I go to someone's house for dinner, or when I have people over, I expect to serve and be served dessert. Unless I go to my parents' house, where they also rarely eat dessert. Unless they have company or the meal is considered a "dinner" or dinner party or something like that.

So, in my family, we knowingly break a rule about the proper components of a specific meal (dinner), but only under certain circumstances (no other guests besides immediate family).

But, does the absence of dessert at my parents' house say something deeper about the nature of our relationship? I mean, since I grew up not eating dessert at home, I don't notice it so much, but there are other things that my mom does wrt breaking the rules of what counts as a meal. Does that mean she'd just rather have a "drinks-only" kind of relationship with her kids?

Oh, man -- have the psychoanalysts discovered Mary Douglas yet?!