noun
1. : the musical form of a sonata used not only in the sonata proper but also in the concerto, symphony, and string quartet and other chamber music
2. : a type of musical structure distinctive of the first movement of the sonata usually based on two themes or subjects presented in different keys often with transitional episodes and consisting of an exposition giving the principal subject in the tonic key and the secondary subject usually in the dominant key if the tonic key is major but otherwise in the relative key, a development giving a full thematic working out of one or both subjects, and a recapitulation repeating both subjects in the original key and ending with a coda