Question

What is the difference between a defined and an undefined term in Geometry?

Answer 1

why are line segment and ray not considered undefined?

Answer 2

"In Euclidean Geometry, the terms point, line, and plane are accepted as intuitive ideas and are not defined. These undefined terms are then used in definitions of other terms such as segment and ray." from Geometry by Jurgensen, Brown, Jurgenson

@j`