Groups of three; plural of triad—can refer to three people, things, or concepts grouped together, or to organized crime groups.
From Greek 'trias' meaning group of three, from 'tri' meaning three. In English, refers to any grouping of three, but gained association with Chinese organized crime syndicates in the 19th century.
The triadic structure is oddly powerful in culture—three acts in storytelling, three wishes in fairy tales, three-person groups feel somehow more stable than pairs—and mathematicians call three the minimum number needed to create geometric complexity.
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