A novel is a long prose narrative that describes fictional characters and events in the form of a sequential story, usually. The genre has historical roots in the fields of medieval and early modern romance and in the tradition of the novella. The latter, an Italian word used to describe short stories, supplied the present generic English term in the 18th century. Further definition of the genre is historically difficult. The construction of the narrative, the plot, the relation to reality, the characterization, and the use of language are usually discussed to show a novel's artistic merits. Most of these requirements were introduced to literary prose in the 16th and 17th centuries, in order to give fiction a justification outside the field of factual history.