This is the 495th most frequent Vietnamese word.
khoa
"Faculty," "department," or "branch" (in an academic or institutional context).
In this sentence, 'Khoa' is used as a proper noun, referring to a person's name.
Khoa là một sinh viên giỏi.
Khoa is a good student.
Here, 'khoa' refers to a department or faculty in an educational institution.
Tôi đang học tại khoa Công Nghệ Thông Tin.
I am studying at the Information Technology department.
In this context, 'khoá' (a variant of 'khoa' with accent mark) is used as a verb meaning 'to lock'.