Rondo
In music a rondo is a piece of music which has one main theme, which is heard several times, and other musical ideas in between each time.  If we give the main theme a label "A" and the other musical ideas "B", "C", "D" etc. then the form of a rondo can be described as ABACADA.  The sections in between the main "A" section are called "episodes".  Rondos can vary in length, e.g. a rondo might be ABACADAEAFA.  Each episode is normally in a different key from the main key.