Triád

Triád is a term used in several languages to denote a group of three and may refer to different concepts in music, criminology, and the social sciences. Etymologically, it derives from a prefix meaning three, combined with a suffix forming a noun.

In music theory, a triad is a chord built from three distinct notes, typically by stacking two intervals above a root note. The common types are major, minor, diminished, and augmented triads. A major triad consists of a root, a major third, and a perfect fifth; a minor triad uses a minor third instead of the major third; diminished and augmented triads alter the fifth accordingly. Triads can appear in root position or in inversions (first inversion with the third in the bass, second inversion with the fifth in the bass). They form the harmonic basis of many Western tonal pieces and are named by their root notes, for example a C major triad (C–E–G) or A minor triad (A–C–E).

In criminology, the Triads refer to organized crime groups with origins in China and Chinese communities, historically described as secret societies or guilds. The term has spread to describe similar criminal networks worldwide. Triads are characterized by coded rituals, hierarchical structures, and involvement in activities such as drug trafficking, extortion, and money laundering. Their influence and methods vary by region and over time.

Beyond these, triad denotes any set of three interconnected elements in fields like sociology (social triads and triadic closure) and semiotics (triadic models, such as the sign–object–interpretant framework).