This is the 7117th most frequent Chinese word.
社会学
The study of human society, social behavior, and social institutions.
In this sentence, "社会学" refers to the academic discipline and is used as the object of the verb "主修" (to major in).
我在大学主修社会学。
I majored in sociology in university.
Here, "社会学" is used as the subject of the sentence and signifies the field of study concerned with human societies.
社会学研究人类群体的行为和社会结构。
Sociology studies human group behaviors and social structures.
"社会学" in this context is utilized to describe an analytical perspective or approach tied to the study of sociology.