If is a simple closed curve in , then has two components (an ``inside'' and ``outside''), with the Boundary of each.
References
Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, p. 9, 1976.
数学辞典收录了8975条数学词条,基本涵盖了常用数学知识及数学英语单词词组的翻译及用法,是数学学习的有利工具。