duplex

American  

[doo-pleks, dyoo-] / ˈdu plɛks, ˈdyu- /

noun

1. duplex apartment.

2. duplex house.

3. paper or cardboard having different colors, finishes, or stocks on opposite sides.

4. Printing.

   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.

5. Genetics. a double-stranded region of DNA.

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adjective

1. having two parts; double; twofold.

2. (of a machine) having two identical working units, operating together or independently, in a single framework or assembly.

3. 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)

1. to make duplex; make or change into a duplex.

   Many owners are duplexing their old houses for extra income.

duplex British  

/ ˈdjuːplɛks /

noun

1. a duplex apartment or house

2. a double-stranded region in a nucleic acid molecule

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adjective

1. having two parts

2. machinery having pairs of components of independent but identical function

3. permitting the transmission of simultaneous signals in both directions in a radio, telecommunications, or computer channel

Other Word Forms

• duplexity noun

Etymology

Origin of duplex

1810–20; < Latin: twofold, double, equivalent to du ( o ) two + -plex -plex

Explanation

A two-family house can be called a duplex. Living in a duplex is great — unless the people with whom you share a wall like to have all-night yodeling parties. In the U.K. a duplex is an apartment with an upstairs and a downstairs, but in North America a duplex is a building divided into two separate living spaces. Most duplexes are built with the two homes side by side, although you can also live in a duplex with apartments on two floors. The Latin duplex means "twofold," from duo, "two," and -plex, "to intertwine." The word was coined in the U.S. around 1922.

Example Sentences

We lived in a two-story duplex built in 1899, where I enjoyed sitting on our enclosed porch watching thunderstorms and the leaves change on trees.

From The Wall Street Journal • Apr. 14, 2026

As he rolled up in front of my Van Nuys duplex, his teal Ford Tempo shimmering in the speckled fall sun, a wave of first-date excitement flooded my system.

From Los Angeles Times • Apr. 3, 2026

“Thank you for the times when we were well and happy and busy,” Dad prayed over the turkey dinner Karen made for the three of us at his Iowa duplex in November.

From The Wall Street Journal • Dec. 4, 2025

But cleaning a house that size was a massive undertaking, and it seemed impossible to keep track of everyone’s belongings, as compared with when they lived in a smaller duplex.

From MarketWatch • Nov. 21, 2025

Diego parked Please Start in front of the duplex.

From "We Are the Ants" by Shaun David Hutchinson