From Latin triad-, stem of trias ("three, triad"), from Ancient Greek τριάς.

Sense 3 (“branch of a Chinese underground criminal society”) is due to the word being applied by the British authorities to underground society in Hong Kong based on the geometry of the Chinese character, derived from a name used by some of those societies, 三合會, referring to the union between heaven, earth, and humanity.

• IPA: /ˈtɹaɪ.æd/

triad (plural triads)

1. A grouping of three.

   Synonyms: threesome, trine, trinity, trio, triplet, troika, triumvirate, Thesaurus:trio

2. A word of three syllables.

   Synonyms: trisyllable

   • 1815 February 23, [Walter Scott], chapter 13, in Guy Mannering; or, The Astrologer. […], volume (please specify |volume=I to III), Edinburgh: […] James Ballantyne and Co. for Longman, Hurst, Rees, Orme, and Brown, […]; and Archibald Constable and Co., […], →OCLC ↗:

     In his general deportment he was pompous and important, affecting a species of florid elocution, which often became ridiculous from his misarranging the triads and quaternions with which he loaded his sentences.

3. A branch of a Chinese underground criminal society, mostly based in Hong Kong.
4. (electronics) On a CRT display, a group of three neighbouring phosphor dots, coloured green, red and blue.
5. (music) A chord consisting of a root tone, the tone two degrees higher, and the tone four degrees higher in a given scale OR any chord with three notes.

• French: triade, trio
• German: Triade
• Italian: triade
• Russian: триа́да
• Spanish: tríada

• German: Dreiklang

• French: triade
• German: Triade
• Italian: triade
• Russian: триа́да