These three parts of sonata-form with their usual subdivisions are:
I. Exposition
(1) Principal theme (or first subject).
(2) Link-episode (or modulation group).
(3) Secondary theme (or song group), always in a nearly related key.
(4) Closing group.
(5) Coda.
II. Development Section
Treating the themes introduced in the exposition in an almost infinite variety of fashions, according to the principles of thematic development. (See [Sec. 148]).