Quadruplex

Part of speech: noun

Definitions

1. A building divided into four separate residential units, or a communication system capable of transmitting four signals simultaneously
2. A structure consisting of four distinct living spaces or a technological framework designed to relay four independent data streams at once
3. An architectural design featuring four separate units for habitation or a network setup that allows for the simultaneous transfer of four signals

Etymology: The Latin "quadruplex" meant "fourfold" or "quadruple," and it was built from "quattuor," the word for "four," joined to "plico," meaning "to fold." Put together, the parts describe something folded four times over, a sense that stayed close to the literal in Latin. The English word carries that arithmetic into two quite different settings: a house with four separate homes inside one structure, and a telegraph or telecommunications system able to send four messages down a single line at once. The second meaning is the one that reveals how the word is used in practice. Multiplexing, the trick of combining several signals so they share one channel, is what "quadruplex" describes at its most specific: four signals carried together rather than one after another. Both senses keep the core idea of quadrupling, whether of people under one roof or messages on one wire.