三個月,學期
Trimester \Tri*mes"ter\, n. [L. trimestris of three months; tri- (see {Tri-}) + mensis month: cf. F. trimestre.] A term or period of three months.
trimester n 1: a period of three months; especially one of the three three-month periods into which human pregnancy is divided 2: one of three divisions of an academic year