[ dahy-ohd ]
/ ˈdaɪ oʊd /
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noun Electronics.
a device, as a two-element electron tube or a semiconductor, through which current can pass freely in only one direction.


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Origin of diode

First recorded in 1919; di-1 + -ode2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What is a diode?

A diode is a device for controlling electrical currents so that they only flow the desired way (the way the engineer wants them to).

Diodes are used in all kinds of electronic devices. Most diodes in use today are semiconductor diodes. People often simply use the word diode when they are talking about a semiconductor diode. A semiconductor is a material that electricity can travel through, but not as well as when it travels through a stronger conductor like copper. This kind of diode is kind of like a door for electricity to move through, but it only opens one way.

Among the simplest kinds of this device are p-n junction diodes. Such diodes are commonly made from the semiconductor silicon. Silicon doesn’t conduct very well on its own, but its conductivity can be improved by adding other elements. Depending on what you add to the silicon, it can become either what’s called a p-type material, which has a positive charge, or an n-type material, which has a negative charge.  To create the diode, some p-type material and n-type material are put together. The p-type is the anode, and the n-type is the cathode. At the junction, where the two materials meet, they cancel each other out, and the area around the junction doesn’t have a charge. The electrical current can’t cross it. If you add a positive electrical current to the positive end and a negative one to the negative end, the junction gets smaller and electricity can flow across the junction. But if you reverse that, the junction gets bigger and the current can’t go across. So electricity can only be conducted in one direction, and the diode is created.

Another basic type of diode is the thermionic diode. You might know these better as vacuum tubes. Vacuum tubes use glass tubes to create a vacuum surrounding a tiny wire, which heats up the cathode and releases electrons. The anode then attracts the electrons, which means the current goes in that direction. Though this type of diode was common in early electrical applications, it’s largely been replaced by the semiconductor type today.

The term LED (as in LED lights and LED bulbs) stands for light-emitting diode. Some semiconductor diodes are so flexible and powerful that they can be made to produce light. This makes LED bulbs more efficient than standard light bulbs.

Example: The device malfunctioned due to a faulty diode, but it was easy to replace.

Where does diode come from?

The first record of the word diode as a noun in an electrical context is believed to come from a 1919 article by engineer William Henry Eccles, who used the word as term for a “tube with two electrodes.” It is a combination of di-, meaning “two,” and -ode, which means “way” or “road” and is used in many electrical and electronics terms, including anode, cathode, and electrode.

Based on its etymology, it sounds like a diode is a two-way street for electrical currents. However, in practice, the typical function of a diode is to control electrical current so that it flows in one direction.

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What are some synonyms for diode?

What are some words that share a root or word element with diode

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How is diode used in real life?

Diodes are very commonly used in many different kinds of electronics, but the word itself is typically only used in technical contexts.


Try using diode!

True or False? 

Many diodes are semiconductor diodes.

How to use diode in a sentence

British Dictionary definitions for diode

/ (ˈdaɪəʊd) /

a semiconductor device containing one p-n junction, used in circuits for converting alternating current to direct currentMore formal name: semiconductor diode
the earliest and simplest type of electronic valve having two electrodes, an anode and a cathode, between which a current can flow only in one direction. It was formerly widely used as a rectifier and detector but has now been replaced in most electrical circuits by the more efficient and reliable semiconductor diode

Word Origin for diode

C20: from di- 1 + -ode ²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for diode

[ dīōd′ ]

An electrical device with two active terminals, an anode and a cathode, through which current passes more easily in one direction (from anode to cathode) than in the reverse direction. Diodes have many uses, including conversion of AC power to DC power, and the decoding of audio-frequency signals from radio signals.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.