peripheral
adj
1 ~ (to sth) of secondary or minor importance (to sth) 次要的; 不重要的
topics peripheral to the main theme 围绕中心议题的小题目.
2 of or on a periphery 外围的; 边缘的
peripheral zones 边缘地带.
Of course he is. He's very successful. He's made lots of records. They broadcast a programme of his music last month on the radio. Why don't you come on Saturday? I think you'd enjoy it.