This paper etches an historical panorama of the notion of the Imaginary. The use as a noun of the adjective (for which an equivalent is now in use in most European languages) developed at the end of the 19th century, but the theoretical apparatus using the term dates from the 40s and 50s. After Sartre, Bachelard, Blanchot, Lacan (and then many others) grabbed hold of a term which has since become a key word of the human sciences at the acme of their prestige. After the « hunt on the imaginary » set forth by the Theory of the 60s and 70s, and the banalisation of the term, it seems to be declining in use in contemporary academia. Such is the moment chosen by the industries of the imaginary to start on its « modelisation ».