三学期制的英文：
trimester system

trimester是什么意思：
n. 三个月,学期

Some women experience morning sickness during the first trimester of pregnancy.
有些妇女在怀孕的头三个月里,早上有恶心感。

system是什么意思：
n. 体系，系统；设备；制度；方法；身体；次序

Is the system unstable?
是系统不稳定吗？

It was not a perfect system.
它不是一个完美的系统。

This is a sexpartite system.
这是一个由六部分组成的系统。

Anatomically, the nervous system is divided into the central nervous system and the peripheral nervous system.
解剖学上把神经组织分为中枢神经系统和周围神经系统。

disaccord between the economic system and political system
经济体制与政治体系间的不协调