A dorm is a building, or a big shared room, where students sleep at school, college, or camp. It is the short, everyday American word for dormitory. In the United States, “the dorm” is where you live on campus: a corridor of small rooms, a shared bathroom, a lot of noise at night. British English more often says halls or halls of residence for college living, though British people still understand dorm, especially for a room with many beds — a school dormitory, a hostel, a camp cabin. It is informal. You would write dormitory in a careful brochure; you would say dorm to a roommate. Though actually, people stretch it: “dorm living” can mean that whole student-house life, not only the walls. You almost always hear it with the: “back at the dorm.”