operetta
1
  (An example of) amusing plays in which many or all of the words
  are sung to music and which might include some dancing.
                 a Gilbert and Sullivan operetta [C]
2
  A theatrical production that has many of the musical elements of opera
  but is lighter and more popular in subject and style and contains spoken dialogue.  NONCOUNT N
                 Operetta is usually less serious and more light-hearted than opera.