Analysis of information sources in references of the Wikipedia article "Prequel" in English language version.
Prequels focus on the action that took place before the original narrative. For instance, in Star Wars: Episode III – Revenge of the Sith the audience learns about how Darth Vader originally became a villain. A prequel assumes that the audience is familiar with the original—the audience must rework the narrative so that they can understand how the prequel leads up to the beginning of the original.
A sequel and prequel to the first film
Aficionados of the original series of five films will know that a prequel already exists, namely Conquest Of The Planet Of The Apes.
Lester may also have locked up the dubious distinction of inaugurating the term 'prequel' in 1979 when he directed 'Butch and Sundance: The Early Days.'
Thus The Silmarillion is at once the precursor of and the sequel to The Lord of the Rings — a curious situation, for which he himself, when badgered for a definition of the relation between the two books, coined the highly uncharacteristic word 'prequel'!
Conquest is in a separate category of films as it serves as both a sequel to the previous film and a prequel to the first two films.
Aficionados of the original series of five films will know that a prequel already exists, namely Conquest Of The Planet Of The Apes.