Boyi refers to the first year of doctoral students, and Yan Yi refers to the first year of graduate students. According to China's current education management system, doctoral students are managed by a loose tutor with students. Students attend classes in the first year, and study papers with tutors in the second and third years. The number and quality of papers reach a certain standard, and you can graduate through defense, so doctors usually graduate in four years. The first year of graduate students is also a class for students to study, and the master's degree is basically three years.