Literature (from Latin litterae (plural); letter) is the art of written works, and is not bound to published sources (although, under circumstances unpublished sources can be exempt). The word literature literally means "acquaintance with letters" and the pars pro toto term "letters" is sometimes used to signify "literature," as in the figures of speech "arts and letters" and "man of letters." The two major classifications of literature are poetry and prose.
"Literature" is differentiated from popular and ephemeral classes of writing. Terms such as "literary fiction" and "literary merit" are used to distinguish individual works as art-literature rather than vernacular writing, and some critics exclude works from being "literary", for example, on grounds of weak or faulty style, use of slang, poor characterization and shallow or contrived construction. Others exclude all genres such as romance, crime and mystery, science fiction, horror and fantasy. Pop lyrics, which are not technically a written medium at all, have also been drawn into this controversy.