say it: TREE-oh
trio is a noun meaning "the cardinal number that is the sum of one and one and one". It carries 5 recorded senses.
a musical composition for three performers
three performers or singers who perform together
three people considered as a unit
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 trio 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.