A radical is the portion of a kanji that is used to list that kanji in a kanji dictionary. It could represent the "general" meaning (whatever that is), it could represent the sound, or it could represent other things that I don't know.

I don't think we can know what the radical is for a new kanji just by looking at it. Although I learned many kanji, I didn't find any pattern whatsoever in what the radical for a kanji has to be.

All this confusion is making me ask this: where does the concept of kanji radical come from to begin with? And more importantly, why isn't there a single definition for it? The reason I am asking this is because while I can see that radicals are NOT the simplest building blocks of all kanji (which is what I thought before), they are still somehow supposed to help us break down the kanji for study and looking up in dictionary. How exactly are they helpful at all with all the chaos in Japanese?

  • By looking at a new kanji~~ >> Ohhh right I can't either. After learning many Kanji~~ >> Ohhh right I didn't either. (日本人だけど・・・)
    – user1016
    Commented May 5, 2013 at 0:52
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    It would probably be useful if you could add some examples of kanji where you find the radical nonintuitive.
    – dainichi
    Commented May 5, 2013 at 7:51
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    Let me be more elabore. Take these 3 kanji 創造物 . There are different ways to break down each of the three Kanji characters. Each kanji can have only 1 radical but there is no rule (as far as I know) that tells us which part is the radical. e.g The 物 has radical 牛 and not 勿. This is where the problem lies. Than there are kanji in which the radical turns out to be something that is not even anything like what we find in the character itself! I see onl chaose here. That is why I have put this question here.
    – quantum231
    Commented May 7, 2013 at 16:34
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    Kanji radicals are not supposed to help you study the kanji. No one invented them in order to be helpful to you. They are a little chaotic - the whole Japanese writing system has developed chaotically. This site gives you the etymology of most kanji: kanjinetworks.com/index.cfm
    – Billy
    Commented Jul 6, 2013 at 0:49

1 Answer 1


The choice of radicals (部首{ぶしゅ}) as in the dictionary radicals (as opposed to any other selection of components), comes from Chinese and presumably was adopted alongside the kanji themselves.

The first source to use radicals was a second-century Chinese dictionary called Shuōwén Jiězì (說文解字 - in Japanese 説文解字{せつもんかいじ}). This included 540 radicals. The set of 214 radicals popularly used today are often called Kangxi radicals from the name of a standard Chinese dictionary of the 18th century which used them (but they were used in earlier works). There is more discussion on the Kangxi radicals in an earlier question here. The Kangxi radicals are generally used to be consistent, but there could be lots of ways of splitting up the characters. Simplified Chinese uses a set of 187 radicals (Xinhua Zidian radicals), for example.

The point of the radicals was never to tell you what the meaning of a character was, but to simply provide a way of indexing. Using a paper dictionary, if the characters are indexed by radical rather than sound it is possible to look up characters you don't know the reading of (even if you have to check a couple of possibilities). When using a physical dictionary, that's quite useful and saves time.

With computers there are other methods to find kanji, even when you can't copy-paste or don't know the reading (multi-radical/component search, handwriting input), so knowing what the dictionary radical is becomes less important.

There are still many cases where there are obvious patterns, and these can help particularly when remembering how to write a kanji. e.g. 金 on left hand side is normally related to metal in some way - names of metals or things made out of metals - 金、銀、鉛、鈴、銅、鍵、etc.

Many body parts have 月 in (in these kanji this radical was 肉 originally and is sometimes called 肉月), as can be seen in 肺、臓、胆、肝、脚、胴, etc, and I believe in this case it's pretty much always on the left hand side.

Or how about 犭? Actual beasts (猪・狼・猿・猫), kanji with a connection to hunting (狩, 猟、 狙, 獲 ), and kanji that you can connect metaphorically to beasts (犯 and 猛, for example), all feature.

You don't have to know the names of all the radicals or what they originally "meant" (in many cases the exact origin of a kanji is not 100% clear anyway), but being aware of common components can provide a sort of memory hook for those cases where there's some sort of connection between the components and either the meaning or reading of the kanji.

  • But if radicals were introduced to index than OPs question is even more valid: why the radical cannot be determined just by looking at the character?
    – macraf
    Commented Nov 13, 2017 at 0:29
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    It's basically like creating a dictionary sorted alphabetically, but placing under A the words: "apple" (because it starts with A), "car" (because the only vowel is A), "position" (because it rhymes with "addition" starting with A), and "squirrel" (just because).
    – macraf
    Commented Nov 13, 2017 at 0:44

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