三个单词均有边界的含义。相比较，border强调地区分界， 多含有边境特征，如河流或山川，其含义粗略，没有boundary 所指的精确，且由于河流或山川的改变border也可能发生变化[1]，如：cross the border into Canada。而 boundary 则多指领土所能达到的最远之疆界划分，其相当精确，可经条约在文件或地图上进行修改，常强调一种理论上的分界[2], 如 By international agreement，the boundary of each nation fronting a body of water extends exactly three miles from the coastline。frontier 为一国际法术语，常指两国边界，指某国沿着另一国border那部分的领土区域，因此可以说它是从一种内部的角度去理解和看待border, 包括了比作为“边界线”的boundary更广泛的区域[3]。
    
[1] "Border often suggests a territorial feature，such as a river or mountain range, and hence is not as precise as boundary. ”Cf. The Editors of The Reader's Digest, Use the Right Word, at p. 61, The Readers Digest Association Proprietary Ltd. (1971).
[2]“A theoretical line that marks the limit of an area of land. " Cf. Linda Picard Wood, J. D. Meniam Webster's Dictionary of Law f at p. 58, Meniam-Webster, Incorporated Springfield, Massachusetts (1996).
[3]“In international law, that portion of the territory of any country which lies close a- long the border line of another country，and so fronts or faces it. The term means something more than the boundary line itself, and includes a tract of strip of country, of indefinite extent, contiguous to the line. ”Cf. The Publisher's Editorial Staff, Black's Law Dictionary, abridged 6th edition, at p. 461 , West Publishing Co. (1991 ).