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.

---

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

• 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

A duplex fad is spreading among the city’s developers.

From The Wall Street Journal • May 11, 2026

The billionaire appears to have purchased the 7,500-square-foot duplex, inside a storied New York building, in an off-market deal.

From The Wall Street Journal • Apr. 29, 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

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

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