The Difference between Deer and Reindeer

The other day Ryan mentioned that he saw a deer outside the window during Music class.  He described the deer in detail, and I could sense his awe by the way he spoke.  Then he commented that deer were neat.  I agreed.  He said, "Reindeer are neat too." Next he pondered, "What's the difference between a deer and a reindeer?  Before I could reply, he exclaimed, "Oh, I know! Reindeer can fly, deer cannot." Thanks Rudolph.