Explain the difference between a undefined term and defined term
in geometry

The difference between defined and undefined terms is that the defined terms can be combined with each other and with undefined terms to define still more terms.These are undefined terms:1.plane 2.point 3.line. 
These are defined terms:1.ray 2.union of sets 3.space 4.subset 5.set 6.proper subset 7.opposite 

1. 3/6 or 1/22. 1/123. 1/84. 1/105. 2/12 or 1/6