You know we learned about sizes in kindergarten. There are 3 simple differentiations.  There is a small, medium, and large. If you don’t have one of them, there are only 2 (a little subtraction for you guys right). That means you cant have a medium. Definitions for medium states from Dictionary.com:

1.a middle state or condition

You need at least 3 items to have one in the middle, that makes it MEDIUM. Note the size comparison they put up for you so you know what a large is. That’s like SUPER large, its 3 times the size of the “medium”. Its no wonder we Americans (me included) are so fat. We can’t tell the difference between, too little and HOLY CRAP that’s a lot of food.