The quarter system is the division of the academic year into three equal parts. Each quarter is 10 weeks in length, and there are usually three quarters (fall, winter and spring) per academic year. All UC campuses, except UC Berkeley and UC Merced, are on a quarter system. In the UC system, three quarters constitute an academic year. A semester is the other type of term within an academic year. Each semester is 18 weeks in length, and there are two semesters (fall and spring) in an academic year. Summer session and intersession (between terms) are available at some campuses.