Definition of "Relationship" :

noun: a relation between people; (relationship' is often used where relation' would serve, as in the relationship between inflation and unemployment', but the preferred usage of relationship' is for human relations or states of relatedness)

"The relationship between mothers and their children."

noun: (anthropology) relatedness or connection by blood or marriage or adoption

noun: a state of connectedness between people (especially an emotional connection)

"He didn't want his wife to know of the relationship."

noun: a state involving mutual dealings between people or parties or countries