Which opera  Pelléas et Mélisande and Die schweigsame Frau has fewer acts ?
Pelléas et Mélisande (opera) Pelléas et Mélisande ("Pelléas and Mélisande") is an opera in five acts with music by Claude Debussy. The French libretto was adapted from Maurice Maeterlinck's Symbolist play "Pelléas et Mélisande". It premiered at the Opéra-Comique in Paris on 30 April 1902 with Jean Périer as Pelléas and Mary Garden as Mélisande in a performance conducted by André Messager, who was instrumental in getting the Opéra-Comique to stage the work. The only opera Debussy ever completed, it is considered a landmark in 20th-century music.
Vénus et Adonis Vénus et Adonis is an opera ("tragédie en musique") in a prologue and 5 acts composed by Henri Desmarets to a libretto by Jean-Baptiste Rousseau. Based on the story of Venus and Adonis in Book X of Ovid's "Metamorphoses", it was first performed by the Académie Royale de Musique at the Théâtre du Palais-Royal in Paris on 28 July 1697 with Marie Le Rochois and Louis Gaulard Dumesny in the title roles. Desmarets staged a major revival of the work with a new prologue at the court of Leopold, Duke of Lorraine in 1707. During the composer's lifetime, it was performed in Germany, Belgium, and France, but then fell into obscurity. Its first staging in modern times took place at the Opéra de Nancy on 28 April 2006.