A definition of a Set by mentioning a defining property.
References
Russell, B. ``Definition of Number.'' Introduction to Mathematical Philosophy. New York: Simon and Schuster, 1971.
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。