Intimacy; a close, friendly relationship or the state of being closely acquainted (na-adjective).
長年の付き合いで二人はとても親密になった。
After years of association, the two became very close.
彼らは親密な会話を交わして秘密を共有した。
They had an intimate conversation and shared secrets.
職場での親密さとプロ意識はバランスが重要だ。
The balance between intimacy and professionalism in the workplace is important.