department of economics; faculty of economics
Refers to the academic unit within a university. In Japanese universities, 学部 can be translated as 'department' or 'faculty' depending on the context.
彼は経済学部の学生です。
He is a student in the department of economics.
経済学部はこの大学で一番人気がある。
The faculty of economics is the most popular at this university.
My older brother entered the economics department last year.
She graduated from the economics department and got a job at a bank.