A pen name (nom de plume, or literary double) is a pseudonym (or, in some cases, a variant form of a real name) adopted by an author and printed on the title page or by-line of his or her works in place of their "real" name. A pen name may be used to make the author's name more distinctive, to disguise his or her gender, to distance an author from some or all of his or her previous works, to protect the author from retribution for his or her writings, to combine more than one author into a single author, or for any of a number of reasons related to the marketing or aesthetic presentation of the work. The author's name may be known only to the publisher, or may come to be common knowledge.
An author may use a pen name if his or her real name is likely to be confused with that of another author or notable individual. For instance, from 1899 the British politician Winston Churchill wrote under the name Winston S. Churchill to distinguish his writings from those of the American novelist of the same name, who was at the time much better known.
Authors who regularly write in more than one genre may use different pen names for each, sometimes with no attempt to conceal a true identity. Romance writer Nora Roberts writes erotic thrillers under the pen name J.D. Robb (such books are titled "Nora Roberts writing as J.D. Robb"); Scots writer Iain Banks wrote mainstream or literary fiction under his own name and published science fiction under Iain M. Banks; Samuel Langhorne Clemens used the aliases Mark Twain and Sieur Louis de Conte for different works. Similarly, an author who writes both fiction and non-fiction (such as the mathematician and fantasy writer Charles Dodgson, who wrote as Lewis Carroll) may use a pseudonym for fiction writing. Science fiction author Harry Turtledove has used the name H.N. Turtletaub for a number of historical novels he has written because he and his publisher felt that the presumed lower sales of those novels might hurt book store orders for the novels he writes under his own name.