An academic term is a period of time in which classes are held at an educational institution. The most common academic terms are SEMESTER, sem, trimester, and TENURE. A SEMESTER is a period of time lasting approximately 16 weeks, while a sem is a shortened version of a SEMESTER, usually lasting 8 weeks. A trimester is a period of time lasting approximately 12 weeks, and TENURE is a period of time in which a professor is employed at an educational institution.