祖率zǔ lǜ

1415926和3.1415927之间，并指出圆周率的约率为22/7，密率为355/113。为了纪念祖冲之，把他算出的近似值叫做祖率。

英the approximate ratio of the circumference of a circle to its diameter as calculated by Zu Chong Zhi;