A secret society is an organization whose activities, events, inner functioning, or membership are concealed. The society may or may not attempt to conceal its existence. The term usually excludes covert groups, such as intelligence agencies or guerrilla warfare insurgencies, that hide their activities and memberships but maintain a public presence.
The exact qualifications for labeling a group a secret society are disputed, but definitions generally rely on the degree to which the organization insists on secrecy, and might involve the retention and transmission of secret knowledge, the denial of membership or knowledge of the group, the creation of personal bonds between members of the organization, and the use of secret rites or rituals which solidify members of the group.
Anthropologically and historically, secret societies have been deeply interlinked with the concept of the Männerbund, the all-male "warrior-band" or "warrior-society" of pre-modern cultures (see H. Schurtz, Alterklassen und Männerbünde, Berlin, 1902; A. Van Gennep, The Rites of Passage, Chicago, 1960).
A purported "family tree of secret societies" has been proposed, although it may not be comprehensive.
Alan Axelrod, author of the International Encyclopedia of Secret Societies and Fraternal Orders, defines a secret society as an organization that:
is exclusive
claims to own special secrets
shows a strong inclination to favor its members.
Historian Richard B. Spence of the University of Idaho offered a similar three-pronged definition:
The group's existence is usually not kept secret, but some beliefs or practices are concealed from the public and require an oath of secrecy and loyalty to learn.
The group promises superior status or knowledge to members.
The group's membership is in some way restrictive, such as by race, sex, religious affiliation, or invitation only.
Spence also proposes a sub-category of "Elite Secret Societies" (composed of high-income or socially influential people) and notes that secret societies have a frequent if not universal tendency towards factionalism, infighting, and claiming origins older than can be reliably documented.