1. (n.) The act of duplicating, or the state of being duplicated; a doubling; a folding over; a fold.

2. (n.) The act or process of dividing by natural growth or spontaneous action; as, the duplication of cartilage cells.

Janus ambiguity ambivalence bedizenment biformity bifurcation burlesque clone conjugation copy counterpart dichotomy ditto double doubleness doublethink doubling dualism duality dummy dupe duplexity duplicate duplication of effort duplicity echo embellishment equivocality expletive extravagance facsimile fat featherbedding filling frill frills frippery gingerbread halving hectography imitation irony knockoff luxury mimeography mock-up model needlessness ornamentation overadornment overlap padding pairing palingenesis paraphrase parody payroll padding plagiarism pleonasm polarity prolixity quadruplicate quotation re-creation re-formation reappearance rebirth rebuilding reconstitution reconstruction recurrence redesign redoing redoubling redundance redundancy reduplication reecho reedition reestablishment refashioning regeneration regenesis regurgitation reincarnation reinstitution reissue remaking renascence renewal renovation reoccurrence reorganization repetition replica replication representation reprinting reproduction reprography reshaping restoration restructuring resumption resurrection return revision revival rubbing superfluity superfluousness tautology tracing transcription travesty triplicate twinning two-facedness twoness unnecessariness verbosity version xerography