affinity
Meaning: a spontaneous feeling of closeness
Usage: Jerry didn’t know why, but he felt an incredible affinity for Kramer the first time they met.
camaraderie
Meaning: brotherhood, jovial unity
Usage: Camaraderie among employees usually leads to success in business.
cordial
Meaning: warm, affectionate
Usage: His cordial greeting melted my anger at once.
gregarious
Meaning: drawn to the company of others, sociable
Usage: The gregarious student enjoyed working with every group in class.
confidant
Meaning: a person entrusted with secrets
Usage: Shortly after we met, she became my chief confidant.
reciprocate
Meaning: to give in return
Usage: When Priya helped Leo study for math, he reciprocated by helping her prepare for history.