tríade

Tríade is a term used in Portuguese to denote a group or set of three related elements. In various disciplines, it is used to describe a unit composed of three parts that together form a recognizable whole. The concept is inherently comparative or classificatory, emphasizing a three-fold relationship rather than a single item.

In music theory, a triad is a three-note chord built by stacking two intervals of a third above a root note. The most common triads are major, minor, diminished, and augmented, and they serve as the basic building blocks of tonal harmony. A triad is typically labeled by its root and quality (for example, C major triad).

In chemistry, the term historically refers to Dobereiner’s triads, groups of three elements with similar properties. In these triads, the atomic weight of the middle element approximately equals the average of the other two, illustrating early attempts at organizing elements by periodic trends.

In physiology, the term triad describes a structural unit in skeletal muscle: a T-tubule flanked by two terminal cisternae of the sarcoplasmic reticulum. This arrangement facilitates rapid calcium release during excitation-contraction coupling.

In criminology and East Asian studies, Triads (often simply called tríades in some languages) refer to Chinese secret societies and organized crime groups. These organizations are typically characterized by hierarchical structures, initiation rituals, and long-standing social networks.

Overall, tríade conveys the idea of three interconnected components across diverse contexts.