A traditional year of college has two semesters, each of which encompasses half the school year. In a semester arrangement, students attend classes for approximately 15 weeks during the fall semester, and then return for 15 weeks in the spring after a winter break.
Some colleges have a modified semester system in which students also take interim courses during May and January. A college also may operate on a trimester or quarterly academic structure as well. A trimester means the academic year is divided into three equal periods rather than two. A quarter system divides the year into four equal terms, with the traditional school year from fall to spring occurring during three of those quarters.