trimester

noun
1
a period of three months during the time when a woman is pregnant
سه‌ماهه, بخش سه ماهه
2
one of the three periods in the year during which classes are held in schools, universities, etc.
سه‌ماهه تحصیلی, دوره سه ماهه, فصل تحصیلی, فصل آموزشی
The school year is divided into three trimesters.
compare semester