一学期,半学年,六个月的时间
Semester \Se*mes"ter\, n. [G., from L. semestris half-yearly; sex six + mensis a month.] A period of six months; especially, a term in a college or uneversity which divides the year into two terms.
semester n 1: one of two divisions of an academic year 2: half a year; a period of 6 months