This is the 9223rd most frequent Korean word.
건축학과를
"Department of Architecture."
건축학과를 is used as the direct object of the verb 졸업하다 (to graduate); it denotes the department that was graduated from.
나는 건축학과를 졸업했어요.
I graduated from the Department of Architecture.
건축학과를 is used as the direct object of the verb 전공하다 (to major); it indicates the field of study being pursued.
제 친구는 건축학과를 전공하고 있어요.
My friend is majoring in the Department of Architecture.
건축학과를 is used in conjunction with 출신으로 (originating from); it specifies the educational context.