The academic year in American universities is usually of a total length of 9 months (excluding a 3-month summer holiday). But the division of these 9 months into terms varies from university to university. Generally, the system will be one of these 3 types:
The Quarter System
In this system the academic year is divided into four quarters of approximately 10 weeks each.
The Trimester System
Here, the academic year is divided into three periods of 12 weeks each.
The Semester System
This is the most common system. In it the educational year is divided into 3 semesters: