The term film noir, French for "black film" (literal) or "dark film" (closer meaning), first applied to Hollywood films by French critic Nino Frank in 1946, was unrecognized by most American film industry professionals of that era. Cinema historians and critics defined the category retrospectively. Before the notion was widely adopted in the 1970s, many of the classic film noirs were referred to as "melodramas". Whether film noir qualifies as a distinct genre is a matter of ongoing debate among scholars.
Film noir encompasses a range of plots: the central figure may be a private investigator (The Big Sleep), a plainclothes policeman (The Big Heat), an aging boxer (The Set-Up), a hapless grifter (Night and the City), a law-abiding citizen lured into a life of crime (Gun Crazy), or simply a victim of circumstance (D.O.A.). Although film noir was originally associated with American productions, the term has been used to describe films from around the world. Many pictures released from the 1960s onward share attributes with film noirs of the classical period, and often treat its conventions self-referentially. Some refer to such latter-day works as neo-noir. The clichés of film noir have inspired parody since the mid-1940s.
The questions of what defines film noir, and what sort of category it is, provoke continuing debate. "We'd be oversimplifying things in calling film noir oneiric, strange, erotic, ambivalent, and cruel "—this set of attributes constitutes the first of many attempts to define film noir made by French critics Raymond Borde and Étienne Chaumeton in their 1955 book Panorama du film noir américain 1941–1953 (A Panorama of American Film Noir), the original and seminal extended treatment of the subject. They emphasize that not every film noir embodies all five attributes in equal measure—one might be more dreamlike; another, particularly brutal. The authors' caveats and repeated efforts at alternative definition have been echoed in subsequent scholarship: in the more than five decades since, there have been innumerable further attempts at definition, yet in the words of cinema historian Mark Bould, film noir remains an "elusive phenomenon always just out of reach".
Though film noir is often identified with a visual style, unconventional within a Hollywood context, that emphasizes low-key lighting and unbalanced compositions, films commonly identified as noir evidence a variety of visual approaches, including ones that fit comfortably within the Hollywood mainstream. Film noir similarly embraces a variety of genres, from the gangster film to the police procedural to the gothic romance to the social problem picture—any example of which from the 1940s and 1950s, now seen as noir's classical era, was likely to be described as a "melodrama" at the time.
While many critics refer to film noir as a genre itself, others argue that it can be no such thing. Film noir is often associated with an urban setting, but many classic noirs take place in small towns, suburbia, rural areas, or on the open road; setting, therefore, cannot be its genre determinant, as with the Western. Similarly, while the private eye and the femme fatale are character types conventionally identified with noir, the majority of film noirs feature neither; so there is no character basis for genre designation as with the gangster film. Nor does film noir rely on anything as evident as the monstrous or supernatural elements of the horror film, the speculative leaps of the science fiction film, or the song-and-dance routines of the musical.