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[doo-pleks, dyoo-] /ˈdu plɛks, ˈdyu-/
paper or cardboard having different colors, finishes, or stocks on opposite sides.
  1. a method of reproducing an illustration using two halftone plates, one black and the other in a color.
  2. a printing press equipped to print both sides of a sheet in one pass.
Genetics. a double-stranded region of DNA.
having two parts; double; twofold.
(of a machine) having two identical working units, operating together or independently, in a single framework or assembly.
pertaining to or noting a telecommunications system, as most telephone systems, permitting the simultaneous transmission of two messages in opposite directions over one channel.
verb (used with object)
to make duplex; make or change into a duplex:
Many owners are duplexing their old houses for extra income.
Origin of duplex
1810-20; < Latin: twofold, double, equivalent to du(o) two + -plex -plex
Related forms
duplexity, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for duplex
Contemporary Examples
Historical Examples
  • The duplex for aeronautical motors is made of cast aluminum alloy.

    Aviation Engines Victor Wilfred Pag
  • The latter is a simple unpolar force, while the former is duplex or polar.

  • It has been practically demonstrated that all organic life must be at least duplex if not multiplex in its constituent elements.

    Parallel Paths Thomas William Rolleston
  • Social progress is for the most part typified by this duplex or polar action.

  • The secondary and tertiary colours, having all duplex relations, may incline without default to either of their relatives.

    Field's Chromatography George Field
British Dictionary definitions for duplex


(US & Canadian) a duplex apartment or house
a double-stranded region in a nucleic acid molecule
having two parts
(machinery) having pairs of components of independent but identical function
permitting the transmission of simultaneous signals in both directions in a radio, telecommunications, or computer channel
Derived Forms
duplexity, noun
Word Origin
C19: from Latin: twofold, from duo two + -plex-fold
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for duplex

1817, "composed of two parts," from Latin duplex, from duo "two" (see two) + -plex, from Greek plax (genitive plakos) "flat surface." The noun sense of "house for two families; two-story apartment" is American English, 1922.

Online Etymology Dictionary, © 2010 Douglas Harper
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duplex in Technology
Used to describe a communications channel that can carry signals in both directions, in contrast to a simplex channel which only ever carries a signal in one direction.
If signals can only flow in one direction at a time the communications is "half-duplex", like a single-lane road with traffic lights at each end. Walkie-talkies with a "press-to-talk" button provide half-duplex communications.
If signals can flow in both directions simultaneously the communications is "full-duplex", like a normal two-lane road. Telephones provide full-duplex communications.
The term "duplex" was first used in wireless, telegraph, and telephone communications. Nearly all communications circuits used by computers are two-way, so the term is seldom used.
The Free On-line Dictionary of Computing, © Denis Howe 2010
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