a speech, etc. at the beginning of a play, book or film that introduces it 序言；序幕；开场白 the Prologue to Chaucer’s ‘Canterbury Tales’ 乔叟的《坎特伯雷故事集》的序诗
Word OriginMiddle English: from Old French, via Latin from Greek prologos, from pro- ‘before’ + logos ‘saying’.