Every act of communication is a relationship.
Good communication and good relationships have the same set of prerequisites.
Humans are born communicators. We start communicating even before birth, and certainly before we achieve any conscious awareness of or control over how we communicate. Many people maintain that lack of awareness and control throughout their lives.
Interpersonal Communication is just about my favorite course to teach. Because the subject is so familiar to the students, the lessons and concepts of the course tend to be shockingly unexpected and self-revealing, and metaphorical lightbulbs tend to flash on all through the semester.
This ought to be a required course for all human beings.