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

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

During that era, DeLorean himself owned a 20-room, $7.2 million Fifth Avenue duplex in Manhattan; a 440-acre, $3.5-million New Jersey estate; and a $4 million California ranch with hot tub accommodations for eight. PEOPLE.com, "Who Was John DeLorean, Disgraced ’80s Auto Mogul Arrested for Smuggling $24 Million of Cocaine?," 7 June 2019 By Antonia Noori Farzan | The Washington Post On the afternoon of Nov. 18, 1993, 9-year-old Angie Housman stepped off the school bus and began walking the half-block to her parents’ duplex in St. Ann, Missouri. The Washington Post, The Mercury News, "A 9-year-old’s murder stumped police for 25 years. Her killer may have been hiding in plain sight.," 6 June 2019 The victim told 911 operators that her boyfriend was intoxicated, armed with a handgun and breaking things inside their duplex. Michael Rietmulder, The Seattle Times, "Man shot dead in Spanaway by sheriff’s deputies who say he was armed, suspected of domestic violence," 21 Oct. 2018 Crime-scene techs placed several lime-green evidence cones just past the side yard, behind the duplexes at the start of a large open grassy field. Laura Mcknight, NOLA.com, "Man shot on Pleasure Street in Desire: NOPD," 25 Jan. 2018 The investigation involved a second search, that at a West Allis duplex at 1414 S. 60th St. That search was executed about 3:10 p.m. Wednesday, June 13, police said. Jane Ford-stewart, Milwaukee Journal Sentinel, "West Allis police, DEA finally catch man linked to 2014 heroin trafficking case," 19 June 2018 Late Sunday morning, there was no outward signs anything was amiss at the white-and-gray duplex. BostonGlobe.com, "DA says woman killed in North Andover was likely strangled," 22 Apr. 2018 The fire started just before 4 a.m. at a two-story duplex in the 4600 block of Brookfield Drive. Dana Hedgpeth, Washington Post, "Man dies in Maryland house fire," 10 Apr. 2018 Fairhurst later moved into a Westport duplex with Charlotte Medeiros and her family, and Charlotte allegedly allowed her to slowly waste away without any medical care. BostonGlobe.com, "Suspects charged in case involving 80-year-old woman who wasted away and died of neglect," 8 May 2018

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

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