(1) 界線，邊界(limiting or dividing line of an area or land)[C]：the～of a country/a park/the school ground/a baseball field國家/公園/學校場地/棒球場的邊界;the～between two countries/my land and hers兩個國家/我的地和她的地之間的界線;(fence/wall/river/gulf) mark/form/be the～of (between)...(籬笆/墻/河/海灣)標志/構成/是……的(……間的)邊界;We have to stay within our country～.我們得待在國界之內(nèi)。a～dispute邊界爭端;〖同〗border，frontier，barrier，edge;
(2) 界線，范圍(outer limit of anything that people think that it has)[C]：push the～ies of knowledge further out把知識的范圍進一步擴大;the～between the possible and impossible可能與不可能之間的界線;The old～ies between subjects are collapsing.學科間的舊界線打破了。
【辨異】boundary與border和frontier的區(qū)別見BORDER。