du·​plex | \ ˈdü-ˌpleks also ˈdyü- How to pronounce duplex (audio) \

Definition of duplex

 (Entry 1 of 3)

1a : having two principal elements or parts : double, twofold
b : having two complementary polynucleotide strands of DNA or of DNA and RNA
2 : allowing telecommunication in opposite directions simultaneously


duplexed; duplexing; duplexes

Definition of duplex (Entry 2 of 3)

transitive verb

: to make duplex



Definition of duplex (Entry 3 of 3)

: something duplex: such as
a : a 2-family house
c : a duplex molecule of DNA or of RNA and DNA

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Synonyms & Antonyms for duplex

Synonyms: Adjective

binary, bipartite, double, double-barreled, double-edged, dual, twin, twofold

Antonyms: Adjective


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Did You Know?

Duplex can describe a confusing variety of things, depending on the technical field. Most of us use it as a noun: a duplex can be either a two-family house or a two-story apartment. In computer science and telecommunications, duplex (or full-duplex) communication can go in both directions at once, while half-duplex communication can go only one way at a time. In other areas, just translate duplex as "double" and see if the sentence makes sense.

Examples of duplex in a Sentence


a duplex apartment with all of the bedrooms on the second floor


We live in the brick duplex.

Recent Examples on the Web: Noun

Black screens used as homicide scenes to block the view of bodies from bystanders were set up in front of a beige duplex on the corner of Josephine and Clara streets Tuesday morning. Emily Lane, NOLA.com, "Man killed in Central City shooting, NOPD says," 6 Feb. 2018 The duplex where Margaret Williams and her cousin lived in Mattapan had no running water, a rodent infestation, and holes in the walls and ceiling. Laura Crimaldi, BostonGlobe.com, "Pam family members go on trial for allegedly scamming elderly siblings out of Mattapan home," 13 July 2018 Okan Tower is planning price tags starting at $318,500 for condo-hotel units, which will be operated as hotel rooms when the owners aren’t there, and at $1.9 million for duplex penthouses. Maya Sweedler, WSJ, "In Miami, a $300 Million Skyscraper Is Banking On Unrest in Turkey," 10 July 2018 The son of the late McDonald’s CEO Jim Cantalupo on Monday sold his four-bedroom, 6,200-square-foot duplex penthouse condo on the 40th floor of a Streeterville high-rise for $5.8 million. Bob Goldsborough, chicagotribune.com, "Son of late McDonald’s CEO sold penthouse condo in Streeterville for $5.8 million," 22 May 2018 And the estate of the noted writer and editor Jean Stein sold her Gracie Square duplex, where Ms. Stein jumped to her death last year. Vivian Marino, New York Times, "Jessica Lange Among Owners Expanding Into Grander Homes," 29 June 2018 In August 2013, Lazarus sold his duplex at 960 Fifth Avenue in Manhattan for $21 million to Peruvian billionaire Carlos Rodriguez-Pastor. Fortune, "Toys 'R' Us Founder Charles Lazarus Dies at 94," 22 Mar. 2018 Chicago Bulls forward Paul Zipser recently paid $730,000 for a three-bedroom, 2,110-square-foot duplex condominium unit in a newer building on the Near West Side, just a few blocks from the United Center and the Bulls’ practice court. Bob Goldsborough, chicagotribune.com, "Bulls forward Paul Zipser buys Near West Side condo for $730,000," 6 Nov. 2017 Well, this past holiday season, many of the homes in their neighborhood were damaged by tornadoes, but Diaz and Cutter were lucky enough to only need repairs on their duplex. Lauren Smith, House Beautiful, "A Demolition Team in Texas Tore Down the Wrong House," 24 Mar. 2016

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'duplex.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of duplex


1567, in the meaning defined at sense 1a


1833, in the meaning defined above


1922, in the meaning defined above

History and Etymology for duplex


Latin, from duo two + -plex -fold — more at two, -fold

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Time Traveler for duplex

The first known use of duplex was in 1567

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More Definitions for duplex



English Language Learners Definition of duplex

: a building that is divided into two separate homes
: an apartment with two floors


du·​plex | \ ˈdü-ˌpleks How to pronounce duplex (audio) , ˈdyü-\

Kids Definition of duplex

: a house with two separate living spaces


du·​plex | \ ˈd(y)ü-ˌpleks How to pronounce duplex (audio) \

Medical Definition of duplex

: a molecule having two complementary polynucleotide strands of DNA or of DNA and RNA

Other Words from duplex

duplex adjective

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More from Merriam-Webster on duplex

Rhyming Dictionary: Words that rhyme with duplex

Thesaurus: All synonyms and antonyms for duplex

Spanish Central: Translation of duplex

Nglish: Translation of duplex for Spanish Speakers

Comments on duplex

What made you want to look up duplex? Please tell us where you read or heard it (including the quote, if possible).


grandiloquent, ostentatious, or bombastic

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