专门 (zhuān mén) as an adverb means 'specially/for a specific purpose' — it's a general, everyday word for doing something intentionally for a reason. 特地 (tè dì) is similar but often implies extra effort or courtesy; 专程 emphasizes traveling a distance for a purpose. As an adjective, 专门 ('dedicated/specialized') contrasts with 专业 (zhuān yè) 'professional', which refers to a field of expertise (e.g. your major).