triads

Triads are terms used across disciplines to denote a set of three related elements. The meaning varies by field, but the common thread is the grouping of three units that interact to produce a larger structure or effect.

In music, a triad is a three-note chord built by stacking a third on top of a root note and a fifth above it. The core types are major (root, major third, perfect fifth) and minor (root, minor third, perfect fifth). Additional varieties include augmented (raised fifth) and diminished (lowered fifth) triads. Triads are the foundation of Western harmony and can appear in root position or inversions, which place a different chord tone in the bass without changing the chord’s quality.

In sociology and social psychology, a triad is a three-person social unit. Dyads involve two people, while triads introduce new dynamics such as coalitions, mediation, or conflict. The concept of triadic closure describes how two people who share a common acquaintance are likely to form a direct relationship, strengthening social networks. Theorists also study balance and coalition patterns within three-person interactions.

In criminology, “Triads” refers to traditional Chinese secret societies that evolved into transnational criminal organizations. These groups have historically engaged in mutual aid and political influence as well as illicit activities such as extortion, fraud, and drug trafficking. Contemporary triads may operate openly in some regions and covertly in others, often with hierarchical lodges and ritual elements.

In semiotics and philosophy, the term appears in Peirce’s triadic model of signs: representamen (the sign), object (that which is signified), and interpretant (the meaning produced in the mind of the interpreter).