inside the department; within the club; the staff
Refers to the interior of a department, club, or organization, or collectively to its members. Often used in contrast with 部外 (outside the department).
That problem should be resolved within the department.
We communicate within the club by email.
We shared the new policy within the department.
Only people within the department know about this matter.
The problem was handled internally within the department.
内部 is a general word for the interior of any organization or thing, whereas 部内 specifically means inside a department or club.
部外 means outside the department or club, the direct opposite of 部内, which means inside it.
Compound of 部 (department, club) and 内 (inside).