trio in WordNet English dictionary

1. the cardinal number that is the sum of one and one and one
   three  3  III  trio  threesome  tierce  leash  troika  triad  trine  trinity  ternary  ternion  triplet  tercet  terzetto  trey  deuce-ace 
   
2. three people considered as a unit
   trio  threesome  triad  trinity 
   
3. a set of three similar things considered as a unit
   trio  triad  triplet  triple 
   
4. a musical composition for three performers
   trio 
   
5. three performers or singers who perform together
   trio