triad Definition

triad
noun

1. Any group of three people or things.
2. music.
A chord that consists of three notes, usually a base note and those notes a third and a fifth above it.
3a. The Western name for any of several Chinese secret societies, especially of the kind that operate in foreign countries and are involved in organized crime, drug-trafficking, extortion, etc.

Form: Triad (sometimes)
Form: Triad Society
3b. A member of such a society.

Form: Triad (sometimes)
4. In Welsh literature: a form of composition where sayings, stories, etc about related subjects are grouped into threes.

Derivative: triadic
adj

Etymology: 16c: from Greek trias group of three.