Commedia dell'arte is a form of theatre characterized by masked "types" which began in Italy in the 16th century and was responsible for the advent of the actresses and improvised performances based on sketches or scenarios. The closest translation of the name is "comedy of craft"; it is shortened from commedia dell'arte all'improvviso, or "comedy of the craft of improvisation". Originally, it was called commedia all'improviso. This was to distinguish the form from commedia erudita or learned comedy that was written by academics and performed by amateurs. Commedia dell'arte, conversely, was performed by professional actors (comici) who perfected a specific role or mask. Italian theater historians, such as Roberto Tessari, Ferdinando Taviani, and Luciano Pinto, believe commedia was a response to the political and economic crisis of the 16th century and, as a consequence, became the first entirely professional form of theater. This is debated though, as evidence shows that there were possibly acting unions prominent as far back as the Greek Times.