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

The difference between defined and an undefined term in Geometry is that defined terms can be combined with each other or an undefined term, and by doing this, there is another term defined. For example, an angle is a combination of two rays, which is an undefined term. Undefined term on the other hand is used to define other terms.  

6/ 11 = 0.545454 so your answer is55%