(1) 界线，边界(limiting or dividing line of an area or land)[C]：the～of a country/a park/the school ground/a baseball field国家/公园/学校场地/棒球场的边界;the～between two countries/my land and hers两个国家/我的地和她的地之间的界线;(fence/wall/river/gulf) mark/form/be the～of (between)...(篱笆/墙/河/海湾)标志/构成/是……的(……间的)边界;We have to stay within our country～.我们得待在国界之内。a～dispute边界争端;〖同〗border，frontier，barrier，edge;

(2) 界线，范围(outer limit of anything that people think that it has)[C]：push the～ies of knowledge further out把知识的范围进一步扩大;the～between the possible and impossible可能与不可能之间的界线;The old～ies between subjects are collapsing.学科间的旧界线打破了。

【辨异】boundary与border和frontier的区别见BORDER。