noun (n)

• the cardinal number that is the sum of one and one and one(noun.quantity)

  Synonym:
  3, deuce-ace, iii, leash, tercet, ternary, ternion, terzetto, three, threesome, tierce, trey, trine, trinity, trio, triplet, troika
  

  source: wordnet30
• a set of three similar things considered as a unit(noun.group)

  Synonym:
  trio, triple, triplet
  

  source: wordnet30
• three people considered as a unit(noun.group)

  Synonym:
  threesome, trinity, trio
  

  source: wordnet30
• a three-note major or minor chord; a note and its third and fifth tones(noun.communication)

  Synonym:
  common chord
  

  source: wordnet30
• A union of three; three objects treated as one; a ternary; a trinity; as, a triad of deities.(noun)

  source: webster1913