triad

noun

• 1a group or set of three connected people or things:the triad of medication, diet, and exercise are necessary in diabetes care
• a chord of three musical notes, consisting of a given note with the third and fifth above it.
• a Welsh form of literary composition with an arrangement of subjects or statements in groups of three.

• 2 (also Triad) a secret society originating in China, typically involved in organized crime.
• a member of a triad.