A circle that separates an area in a plane in which a certain behaviour of a mathematical system occurs from an area where it does not occur.
Late 19th century; earliest use found in Andrew Forsyth (1858–1942), mathematician.
英汉双解词典包含464360条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。