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A diode is a small electrical part that lets electric current go one way, and mostly blocks it the other way. That one-way behaviour is the whole point: people use diodes to turn alternating current into a one-way flow, to protect a circuit, or to make light (an LED is a light-emitting diode).
A diode二極體 is a small electrical part是一種小小的電子元件，that lets electric current go one way能讓電流往一個方向通過，and mostly blocks it the other way另一個方向則大致會被擋住。That one-way behaviour is the whole point這種單向特性就是它的重點所在：people use diodes to turn alternating current into a one-way flow大家用二極體把交流電變成單向電流、to protect a circuit用來保護電路、or to make light (an LED is a light-emitting diode)或用來發光（LED 就是發光二極體）。
It has two ends, or terminals, which is why the English name was built as “two” plus a word for a path or electrode.
It has two ends, or terminals它有兩個端點，which is why the English name was built as “two” plus a word for a path or electrode這就是為什麼英文名字是「二」加上表示路徑或電極的字組成的。
You will meet it in physics class, in electronics, and on diagrams. It is a technical word, not a daily-life one, but it is very common in that world.
You will meet it in physics class, in electronics, and on gadget diagrams你會在物理課、電子學、還有電器的電路圖上遇到它。It is a technical word, not a daily-life one這是個技術用語，不是日常生活的字，but it is very common in that world但在那個領域裡非常常見。
Though actually, a real diode is not a perfect one-way door — a little current can leak the wrong way, and if you push too hard you can break it.
Though actually不過其實，a real diode is not a perfect one-way door真正的二極體並不是一扇完美的單向門——a little current can leak the wrong way還是會有一點電流從反方向漏過去，and if you push too hard you can break it如果電壓太強還會把它弄壞。
組成A learned English formation, coined by William Henry Eccles in 1919, from di- (“two”) + -ode (from Greek hodos, “way, path,” the same piece as in electrode). He was thinking of a part with two electrodes. The older Greek word δίοδος did mean “a passage through,” but that Greek word is dia- (“through”) + hodos, not di- (“two”) + hodos — so the English name is a new build, not a clean copy of the Greek.
原始詞典資料1 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
diodenoun/ˈdaɪ.əʊd/
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businesselectrical-engineeringelectricityAn electronic device that allows current to flow in one direction only; used chiefly as a rectifier.
- I propose to give the name diode to a tube with two electrodes.
- If a crystal or a diode is used, the amplifier-voltmeter combination may be used with an amplitude-modulated source; or with a c-w source, the detector may be connected to a microammeter or galvanometer as an indicating device.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。