intimacy

(noun) close or warm friendship. Synonyms: familiarity, closeness. Example: "The absence of fences created a mysterious intimacy in which no one knew privacy."

(noun) a usually secretive or illicit sexual relationship. Synonyms: affair, affaire, liaison, involvement, amour.

(noun) a feeling of being intimate and belonging together. Synonyms: closeness. Example: "Their closeness grew as the night wore on."