Triad /(?)/

Tri·ad

Triad

n.
  1. A union of three; three objects treated as one; a ternary; a trinity; as, a triad of deities.
  2. A chord of three notes. (Mus.)
  3. An element or radical whose valence is three. (Chem.)

Phrases & Compounds
Triads of the Welsh bards
poetical histories, in which the facts recorded are grouped by threes, three things or circumstances of a kind being mentioned together.
Hindu triad
See Trimurti.