摘要
人们从生活需要逐步发展“数”的理论．从自然数经过分数、零和负数建立了“有理数”这个概念．大家想过古人为什么给这类数取这个名字吗？是因为有理数有理吗？
People developed number theory from demand of daily life, they formed concept of ＂rational number＂ from natural number, fraction, zero and negative number step by step. Have you ever considered why ancestors named this kind of number ＂rational number＂？ Is ＂rational number＂reasonable？
