While on the surface there may seem to be a blending of the meaning of privacy versus confidentiality, from the perspective of psychology, there is a distinct difference. Both of these terms are individually distinct form the concept of privilege as well.
Privacy is the concept that a person’s business, whether emotional, physical, spiritual, financial, legal, and so on are affairs that are left to that individual to divulge to others or not. Maintaining control over this type of information can be crucial to a person’s identity, happiness, and dignity. Confidentiality as a concept broadens out from privacy and holds that if information about one person is given to or found out by another person, there are, at times, expectations that the information will be held in confidence and not released to anyone else without the consent of the initiating individual. This is the type of situation where medical professionals, clergy, and others are privy to information from or about a person but are expected not to broadcast that information.
When the term or concept of privilege is in play, this is where a legal concept is relative. Privilege stems from a person’s right to speak with a legal representative regarding facts and events. The courts decide whether or not that legal representative must or must not relay that information to appropriate members of law enforcement or to the courts themselves. The information at the basis of privilege can be between a legal representative and a client, between married people, and even between parishioners and clergy, although there are exceptions in nearly every pairing listed here.
While the three terms represent differing levels of the same concept, there are formal and legal rules binding their specific definitions. Privacy is something held by the individual; confidentiality is ruled by professional codes of ethics, and privilege is ruled by law.