Film noir is a cinematic term used primarily to describe stylish Hollywood crime dramas, particularly those that emphasize moral ambiguity and sexual motivation. Hollywood's classic film noir period is generally regarded as stretching from the early 1940s to the late 1950s. Film noir of this era is associated with a low-key black-and-white visual style that has roots in German Expressionist cinematography, while many of the prototypical stories and much of the attitude of classic noir derive from the hardboiled school of crime fiction that emerged in the United States during the Depression.
The term film noir (French for "black film"), first applied to Hollywood movies by French critic Nino Frank in 1946, was unknown to most American film industry professionals of the era. Cinema historians and critics defined the canon of film noir in retrospect; many of those involved in the making of the classic noirs later professed to be unaware of having created a distinctive type of film.