Definition of Fun according to Urban Dictionary example #8
The only reason to live, because without it life sucks!
Boy: Hey want to go have some fun?
Girl: Can't, got to do homework.
Boy: WHAT?! Screw homework you can do it later!!
Girl: What will be doing anyway?
*Girl's dad pulls up driveway from work*
Boy: Uuuuuhhh you know what, homework sounds like a good idea right now...
For some people i guess talking about energy and mass is fun. Anyways here's some background music for your conversation