a three-month period

any of the three three-month periods that a human pregnancy is divided into

The second trimester is generally the easiest part of a pregnancy. 一般说来，第二个三月期是怀孕期间最轻松的一段时间。

any of the three-month periods into which the school or college year is sometimes divided

Many students arrange internships or work-study placements during the second trimester. 许多学生在第二学期安排实习或半工半读。