say it: TRAHY-ad
triad is a noun meaning "the cardinal number that is the sum of one and one and one". It carries 4 recorded senses.
three people considered as a unit
a three-note major or minor chord; a note and its third and fifth tones
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for triad come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.