peripheral

/pərˈɪfərəl/

on or near an edge or constituting an outer boundary; the outer area

中文释义：外围的；次要的

The peripheral areas of the city are less developed than the center.

城市的周边地区不如中心发达。

In this debate, that issue is only peripheral to the main argument.

在这场辩论中，那个问题只是主要论点的次要部分。