orchestra
Synonym discussion
Sense: noun/1
For this sense, orchestra is the usual word for a large instrumental group, often one with string players and a conductor. Band is broader and less exact: it can mean a school wind band, a rock group, or many other kinds of music group. Ensemble is a more formal general word for performers playing together, and it often describes a smaller group. Choir is different because the members sing instead of mainly playing instruments. Quartet is specific to four performers. Use orchestra when you mean the full classical-style group itself. You can say Maya plays violin in the youth orchestra, but Maya sings in the school choir names a different kind of group.
Etymology
Orchestra came into English from Latin orchestra, which came from Greek orkhestra. In ancient Greek theatres, the word first named the open area where the chorus performed. English later kept the same form, and the modern music meaning grew from the group that played in the theatre.