/ ˈtriːəʊ; NAmE ˈtriːoʊ/ noun ( pl. -os )
1.
[ C +sing./pl. v . ] a group of three people or things
—compare duo
2.
[ C +sing./pl. v . ] a group of three musicians or singers who play or sing together
3.
[ C ] a piece of music for three musicians or singers :
a trio for piano, oboe and bassoon
—compare duet
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WORD ORIGIN
early 18th cent.: from Italian , from Latin tres three, on the pattern of duo .