Class-friend: a friend that you only see/associate with in class or in a school-related environment.
Your business partner, not your partner-in-crime.
If you have their number, it is most likely because you were in a group project with them. Friends on Snapchat? Then you probably worked on that group project on a Friday afternoon and added them later that night for kicks. Your conversations revolve around class discussions, professors and homework. No, you will not divulge last weekend's expeditions to them, but ranting to them about a looming paper is natural. They are not the person you call when something unfortunate happens and you are freaking out. They are, however, that person you run up to in the library to interrogate about an upcoming test. You compare notes, answers and thesis ideas with this person, but you probably do not even know their middle name.
Class-friends. They have been around forever, but unfortunately rotate out of your life with each passing semester. They existed in high school as well, but I know I for one have not conversed with the majority of my class-friends since graduation. They are the people you always presume to be in your life, but eventually slip out of it. I miss some of my class-friends from high school and it saddens me to know that the most meaningful things I knew about them were their study quirks or GPA.
In some way, shape or form, class-friends continue to be a part of life. Every semester provides a new set of faces: some familiar, others not so much. Most class-friends encompass the same universal set of friendship qualities, though. Understanding and considerate, class-friends feel your pain when it comes to all-nighters and research papers. Again, they are not the person you call to bail you out of jail, but they are the person you text when you are in jail and need someone to send you the lecture notes. Like I said, they are typically pretty understanding.
Hopefully in college I will put a little more effort into becoming actual friends with my class-friends. The first step—learn their middle names.