triad

(noun) the cardinal number that is the sum of one and one and one. Synonyms: three, 3, III, trio, threesome, tierce, leash, troika, trine, trinity, ternary, ternion, triplet, tercet, terzetto, trey, deuce-ace.

(noun) a set of three similar things considered as a unit. Synonyms: trio, triplet, triple.

(noun) three people considered as a unit. Synonyms: trio, threesome, trinity.

(noun) a three-note major or minor chord; a note and its third and fifth tones. Synonyms: common chord.