1.
a connection, association, or involvement.3.
an emotional or other connection between people: the relationship between teachers and students.4.
a sexual involvement; affair.
Okay, fair enough. For a while growing up, I generally only thought of the word relationship in the context of the fourth definition presented above. I blame television and my own naivete. As I grew older, I became more and more aware of the breadth of the word, and it began encompassing the other three definitions. Relationships nowadays for me, encompass more and more the third definition, that is my "default definition", what I automatically think of when I hear the word.