boundary
/ˈbaʊndərɪ/noun
(pl. -ies)
1- a line which marks the limits of an area; a dividing line分界线, 边界; 界限：
a county boundary
县界
the river marks the boundary between the two regions
这条河是这两个地区的分界线
as modifier a boundary wall界墙
1.1
- （常作 boundaries）figurative a limit of something abstract, especially a subject or sphere of activity〈喻〉（某些抽象事物的）界限：
a community without class or political boundaries.
一个没有阶级或政治界限的社区。
1.2
- Cricket a hit crossing the limits of the field, scoring four or six runs【板球】击球超过边界线得分（得4分和6分）。
词源
early 17th cent.: variant of dialect bounder, from BOUND2 + -ER1 , perhaps on the pattern of limitary.