Biology and genetics
* Gene duplication, a process which can result in free mutation * Chromosomal duplication, which can cause Bloom and Rett syndrome * Polyploidy, a phenomenon also known as ''ancient genome duplication'' * Enteric duplication cysts, certain portions of the gastrointestinal tract * Diprosopus, a form of cojoined twins also known as ''craniofacial duplication'' * Diphallia, a medical condition also known as ''penile duplication''Computing
* Duplicate code, a source code sequence that occurs more than once in a program * Duplicate characters in Unicode, pairs of single Unicode code points that are canonically equivalent. The reason for this are compatibility issues with legacy systems * Data redundancy, either wanted or unwanted (in which case one resorts to data deduplication) * Content copying through cut, copy, and paste * File copyingMathematics
* Duplication matrix, a linear transformation dealing with half-vectorization * Doubling the cube, a problem in geometry also known as ''duplication of the cube'' * A type of multiplication theorem called the ''Legendre duplication formula'' or simply "duplication formula"Technology
* Duplicating machines, machines and processes designed to reproduce printed material, photocopying being among the best-known today; see also List of duplicating processes * Loop bin duplicator, a device designed to copy pre-recorded audio tapes * Double track, a method of railway design also known as ''track duplication'' * In Road#Duplication, road construction, conversion of a single carriageway into Dual carriagewayArt and fiction
* Duplicate (1998 film), ''Duplicate'' (1998 film), a Bollywood film directed by Mahesh Bhatt * Duplicate (2009 film), ''Duplicate'' (2009 film), a 2009 Malayalam film *''Duplicates'', a 1992 television film starring Gregory Harrison and Kim Greist * ''The Duplicate'', a 1988 children's book by William Sleater * Batman Duplicate, a villain in ''Batman: The Animated Series'' * "The Duplicate Man", a 1964 episode of ''The Outer Limits'' * The Transmogrifier, duplicator machine in ''Calvin and Hobbes'' * "Duplicate", a song by White Town from ''Peek & Poke (White Town album), Peek & Poke'' * "Duplicates", a song by We Are the Physics from ''We Are the Physics Are OK at Music''Other uses
* Duplicate publication, the publication same intellectual material by the same author twice * Reduplication, a morphological process in linguistics * Duplicate bridge, a popular variant of contract bridge * Duplicate Scrabble, a Scrabble variant popular in French and some other languages * "Decouple, duplicate, discriminate," the "three Ds" articulated by Madeleine Albright as necessary for NATO to avoid * Duplicate, another term for Body double in filmsSee also
* cloning, Clone, the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually * Copy (disambiguation) * Doppelgänger, a paranormal double of a living person *dup (disambiguation) *dupe (disambiguation) * Redundancy (disambiguation) * Symmetry, has two meanings. The first is a vague sense of harmonious and beautiful proportion and balance. The second is an exact mathematical "patterned self-similarity" that can be demonstrated with the rules of a formal system, such as geometry or physics {{disambiguation