In hyperbolic and elliptical geometry ratio of radius and circumference of a circle is not a constant. You can't define pi there as such. Anyway, pi comes up i

In hyperbolic and elliptical geometry ratio of radius and circumference of a circle is not a constant. You can't define pi there as such. Anyway, pi comes up in various fields of math with no relation to the geometry of space we live in. Ironically, pi comes from geometry (land measurement), and the land they measured has elliptical geometry.