duplex

American  

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

noun

• duplexes
  plural

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

Derived Forms

• duplexity
  noun

Inflected Forms

Nouns

• duplexes
  plural

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

See Examples For:

duplex duplexes

Before that, about 10 years ago, he rented a room in a duplex for $333; that same room now rents for $900, he says.

From BBC ● Jul. 18, 2026

When I was 11, we finally settled down and lived in the back of a redbrick duplex with patches of grass and sand—my backyard.

From The Wall Street Journal ● Jun. 16, 2026

“The biggest piece is affordability,” says Rachel Lange-Mills, president of Lange Real Estate, which has built duplex communities.

From The Wall Street Journal ● May 11, 2026

Billionaire Citadel founder and CEO Ken Griffin has reportedly expanded his enormous international property portfolio with the addition of a $38 million duplex apartment inside a storied New York City apartment building.

From MarketWatch ● Apr. 22, 2026

His duplex had changed since the last time she was here, and it was more than just the box of Fisher-Price toys in the living room and the makeup in the bathroom.

From "Eleanor & Park" by Rainbow Rowell

Housing reforms that increase supply, such as allowing smaller lots in new subdivisions, permitting duplexes, townhomes, and backyard cottages on existing lots, and changing zoning laws to allow housing nearer to jobs, are land-use issues.

From Barron's ● Jun. 24, 2026

The measure defines a big institutional investor as an entity that controls 350 homes or more, and its definition of a single-family home includes duplexes along with traditional detached houses.

From MarketWatch ● Jun. 22, 2026

Economists say duplexes are the kind of “light-touch density” that allows cities to add more housing for middle-class families without entirely transforming a neighborhood.

From The Wall Street Journal ● May 11, 2026

Relatedly, duplexes get to use the state’s simple single-family residential code instead of the more demanding guidelines that apply to apartment buildings.

From Slate ● Jul. 31, 2025

Winslow Road was one long line of duplexes, but standing on the curb you would not have known it.

From "Little Fires Everywhere" by Celeste Ng