Source : Webster's Revised Unabridged Dictionary (1913)
Triad \Tri"ad\, n. [L. trias, -adis, Gr. ?, ?, fr.?, ?, three:
cf. F. triade. See {Three}, and cf. {Trias}, {Trio}.]
1. A union of three; three objects treated as one; a ternary;
a trinity; as, a triad of deities.
2. (Mus.)
(a) A chord of three notes.
(b) The common chord, consisting of a tone with its third
and fifth, with or without the octave.
3. (Chem.) An element or radical whose valence is three.
{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}.