relationship" & "relation" is same mean Some doctors think there is a relation/relationship between smoking and lung cancer. John's relation with Mary is father and daughter. ---form type John's relationship with Mary has improved. -----familiar type

This could probably be resolved by just looking at a good dictionary. 'relation' is broader in its meaning and one or more of these meanings can overlap with the meaning of relationship. Usually the word relationship involves interactions between people where relation(s) can sometimes mean involve people but can also be used in more abstract ways. I suggest you look them up and compare. I recommend the Advanced English Dictionary which can be downloaded for free through the Microsoft Store.