緣份 is a noun that refers to an affinity between two people. It's an attraction of souls. Some say it's a predestined relationship. People who "have it" will "click". They get along better, they say the right things, do the right things, cause positive progress in each others' lives.
It's popularly used to describe the relationship between lovers in a time when this special bond is the Holy Grail of singles everywhere. It has lent itself to lyrics, legends and countless literary works, new and classic.
But, it can also describe the connection between teacher and student, mentor and protégé (say "mentee" in front of me and I'll rip your head off), parent and child, siblings, business partners or just regular friends, etc.
|to meet is the beginning of 緣|
|to know each other is the continuation of 緣|
|to reunite time and time again is the establishment of 緣|