exordium

a short section (as of a book) that leads to or explains the main part <in his exordium the author warns his readers that they should expect a radically different interpretation of the causes of the war> Synonyms introduction, foreword, intro, preamble, preface, prelude, proem, prologue (also prolog), prolusionRelated Words beginning, commencement, initiation, opening, origin, origination, outset, startNear Antonyms envoi (or envoy), postscript; aftermath; cessation, close, closing, conclusion, end, finale, finish, stop, terminationAntonyms epilogue (also epilog)