Getting Radical About Radicals – Outlier Linguistics

Getting Radical About Radicals

Getting Radical about Radicals

Why you should think of kanji in terms of functional components.

By John Renfroe

I know this advice is going to rub some people the wrong way, but hopefully by the end of the article you’ll understand why I say this: radicals are of little use for learning how kanji work. Their purpose is indexing kanji in a dictionary.

There’s a huge misconception about how kanji work. You see this sort of advice all the time: “Kanji are made up of radicals, so you should learn the radicals first,” or “Make sure you learn the radicals. They’re the building blocks of kanji.” This is not true. People who say this are well-intentioned but ill-informed about the nature of the kanji.

The word “radical” is best understood as “a kanji component that sometimes plays the role of radical,” NOT “a kanji component that has the nature of being a radical”. For example, 大 【ダイ】 “big” is a component that is on the list of radicals, but that doesn’t mean that 大 is always the radical when it appears in a kanji. A single kanji only has a single radical, no matter how many kanji components it has. And since the choice of which component will play the role of radical is up to the editor of a given dictionary, it may be different in different dictionaries (and may differ between Chinese and Japanese!). And yes, many of the components on the list of radicals do show up a lot in kanji and therefore should be learned, but they should be learned as part of a system of functional components — components which express sound and meaning.

So, if you’re talking about radicals, the conversation should focus on dictionary lookup. If you’re talking about how kanji work, or about etymology, then it should be about semantic and sound components. Getting the terminology straight helps to prevent confusing statements like “radicals are the building blocks of kanji.” They're not. Functional components are.

The concept of radical, or 部首 【ブシュ】 (bushu), didn’t even exist until after the publication of the Setsumon Kaiji (説文解字 【セツモンカイジ】; Shuowen Jiezi in Chinese) in 100 CE, at which point the writing system had already been around for well over 1500 years. The vast majority of kanji in use today were invented before the Setsumon. Read that again and let it sink in. If that’s the case, then there’s no way that “radicals” were what people had in mind when they were creating kanji. There must have been something else going on.

So what are radicals, really?

That’s an interesting question. The word “radical” is really a poor translation of 部首 【ブシュ】 in the first place. Bushu literally means “section head.” Following the model of the Setsumon, kanji dictionaries are traditionally arranged into sections containing similar graphic components. These sections are called 部 【ブ】. The first kanji in that section is the section head (部首 【ブシュ】), or the first of the section. Each kanji in that section is filed under one bushu. Note that I didn’t say the kanji “has” one 部首. It’s an important distinction to make. The kanji is filed under a 部 【ブ】, or section. This is a choice made by the editor of a kanji dictionary, not an inherent part of the nature of kanji.

Which section to file a kanji under can be a fairly arbitrary decision. Most people’s understanding is that the bushu gives a hint about meaning and the sound component (声符 【セイフ】) gives a hint about the sound, and that the two are different entities. That’s not always the case. Sometimes, the bushu is the sound component. For example, 刂 (刀 【トウ】, “knife”) is both the sound component and the radical in 到 【トウ】 “to arrive,” but it is not the meaning component. 至 【シ】 is, and it means “to arrive,” just like 到. Intuitively, one would think that radicals are assigned in a consistent manner, but sometimes the way they’re assigned can be very haphazard, as we've seen.

So again, kanji are filed into a given section. This is a choice made by a human being, not an inherent part of the nature of kanji, and it’s a flawed — but workable — system.

So hopefully, you can see that “radicals” (remember: section headings!) are useful for organising and looking things up in a dictionary, but they’re not especially useful for explaining how kanji work.

But there’s a better way

You should look at kanji in terms of their functional components. Kanji components can serve a few different functions, and you need to understand those functions rather than lump them all under one category called “radicals.”

There are three attributes that all kanji have (using 大 as an example):

  • Form: What is it a picture of? 大 is a picture of a person (specifically, an adult).

  • Meaning: What does it mean? 大 means big, because adults are big in comparison to children.

  • Sound: What is its pronunciation? (Or, if it’s a sound component, what is the range of sounds it can represent?) 大 is pronounced ダイ dai in Japanese (I'm using onyomi here, since those readings are the only ones that are relevant when discussing sound components).

The possible functions that a component can have derive directly from these three attributes.

There are three primary functions:

  • A component can express meaning by way of its form. Example: 大 is a picture of a person, and that is its function in kanji like 美 【ビ】 “beautiful.” 美 is not a “big” 大 “sheep” 羊, but a depiction of a person wearing a headdress (the headdress 𦍌 now resembles 羊, but it's unrelated). This is by far the most common way of expressing meaning.

Other examples of 大 functioning in this way include:

天 【テン】 “heavens” (originally “person with a mark indicating the forehead”)

夫 【フ】 “husband, man”

  • A component can express meaning by way of meaning. Example: 大 means “big,” and it expresses the meaning “big” in kanji like 尖. This is how most people explain all semantic components, but in reality this function is very uncommon!

    • Form: “small” over “big”
    • Meaning: “sharp”
    • Sound: セン sen

As for why “small” over “big” means “sharp,” take a look:


  • A component can express sound. Example: 大 is pronounced ダイ dai in Japanese, and it originally served as the sound component in the kanji 達 タツ、ダ tatsu, da “to arrive”.

Then there is a fourth function that derives from the way kanji evolved in form over time. A component can also:

  • Serve as a placeholder for an earlier form that has now been corrupted (note: that article is for Chinese learners, but the content is relevant; an adapted version of the article for people learning Japanese is forthcoming!).

This one is difficult to ascertain without training in palaeography, but the Outlier Kanji Dictionary explains which components have been corrupted and how. Continuing with 大 as an example, there are 1) instances in which a component was originally 大 but has now changed to something else, and 2) instances in which a component started as something else but has corrupted to look like 大 today (that is, you can’t trust your eyes!).

  1. The sound component in 達 is 𦍒 【タツ、ダ】 tatsu, da. The top part today looks like 土 【ド、ト】 “earth,” but it was originally 大, which was then corrupted over time. An uncorrupted version of this component would look like 羍 today.1


The form above is written in small seal script (小篆【ショウテン】). This is what 大 and 土 looked like in small seal, for comparison:

  1. In the kanji 莫【バク、ボ】 (“do not,” but it originally represented the word “sunset,” which is now written 暮【ボ】), what today looks like 大 on the bottom was originally 艸 【ソウ】 “grass” (there was 艸 on both the top and bottom, and the kanji depicted the sun setting behind the grass), which then corrupted over time to look like 大.

So now you’ve seen how the same component can serve completely different functions in different kanji, and how components can become corrupted over time, obscuring their original purpose. Here’s the interesting thing: out of the kanji I’ve just discussed, 大 is only the radical in 天 and 夫. In the others, it’s not, no matter which function it’s serving. The radical in the other kanji is:






Again, all this is not to say that you should completely throw radicals out the window. They’re good to know, but you should keep in mind what they’re used for: looking up kanji in traditionally-arranged dictionaries. That’s it. They’re not the “building blocks of kanji” (that’s functional components!). They’re an imperfect, man-made system of arranging and looking up kanji in a dictionary. The concept of 部首 didn’t even exist when the vast majority of kanji were being created.

But sound and meaning components did exist. Sound and meaning components are the building blocks of kanji. Sound and meaning components are what people were thinking of whenever they made a new Chinese kanji. When you’re learning a new kanji, thinking in terms of these functional components rather than radicals will clarify a lot of confusing things about kanji. Anything that tells you otherwise is inaccurate and (unintentionally) leading you astray.

  1. 𦍒 is also a meaning component. 达 is a picture of a guy walking across the road. The original meaning was “arrive at point b from point a”. 達 is the same thing, but has a guy leading a sheep from point A to point B.

1 comment

  • Hello. I write today merely to say ‘thank you’ for undertaking this research and making it available via this website, and via mobile apps like KANJI STUDY (for Android), produced by Chase Colburn. Both Outlier content and Kanji Study have been indispensable for my self-education in Japanese, what with having relocated to Japan suddenly a few years ago with only rudimentary formal (classroom) study. Two years later, I’m preparing to sit the JLPT N2 exam. Knowing that I can comprehend kanji more deeply with both Outlier and the accessibility of Kanji Study, I feel very confident in my preparations and chances for success both now and in the future. Thank you to all involved, much love and light and self-awareness to all sentient beings. Gassho.


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