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.

---

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

---

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

My mom was on the top floor of a duplex on a steep hill, and my dad lived in a small house with a white fence.

From The Wall Street Journal ● Jun. 2, 2026

Michael Hull, a retired lettuce farmer, says he is aware of the duplex mania.

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

“We’re living in a duplex now,” my mother explained, and I sensed that we had come up in the world.

From "Three Little Words: A Memoir" by Ashley Rhodes-Courter

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

They watched with alarm as a developer known for building boxy duplexes in South Los Angeles started buying lots on their block in west Altadena.

From Los Angeles Times ● May 21, 2026

On the housing front, rows of affordable duplexes are sprouting up for young families, retirees and empty-nesters next to single-family homes and farmland.

From The Wall Street Journal ● May 11, 2026

It rose deftly from a small neighborhood of duplexes, laundromats, and mom-and-pop restaurants, mostly Korean and soul food.

From "Anger Is a Gift" by Mark Oshiro