being attached to or affiliated with something; belonging to; accompanying.
その病院には小児科が付属している。
That hospital has a pediatric department attached to it.
このアパートは管理人室が付属しているので安心だ。
This apartment comes with a caretaker's office, so it's reassuring.
付属の書類を忘れずに提出してください。
Please don't forget to submit the attached documents.
an attached or affiliated school (often abbreviated); used to refer to a school that is affiliated with a university or other institution.
彼女は東京大学付属の高校に通っている。
She attends a high school affiliated with the University of Tokyo.
付属校の入試は競争が激しい。
Entrance exams for affiliated schools are highly competitive.