The "atomic" kanji components
What is a kanji component?
Most kanji can be broken up into two or more separate shapes, or components, which appear on their own as characters in their own right. For example, the characters 日 sun and 月 moon come together as components in the character 明 bright. Some components don't correspond to any standalone character in modern Japanese usage, but they appear again and again inside multiple characters, like the component 宀 which represents a house, and is used in kanji like 家 household, 室 room, and 宿 lodging.
This means that, even though there are tens of thousands of kanji in existence, they all may be combinations of just a few hundred repeating components
How many kanji components do I need to know?
With the help of data from the Kanji Database project, I've established a list of just 278 components which come together in various combinations to form all the 3,530 most important kanji in everyday modern Japanese.
For each component, I've selected an English keyword based on either its historical meaning, its shape, or the context in which it's used in modern Japanese. Hopefully, these keywords will help you imbue the component shapes with meaning so you can learn to recognize them.
In some cases, a set of components will share a single keyword--you can think of these as variant forms of a single component. If you count a set of variants as a single component, there are just 200 components you have to learn in order to cover all the 3,530 most important kanji.
Why do some components have variants?
For the most part, these variant forms only differ slightly in shape, and there is a logic to which variant is used when. For example, the component 羊 sheep has the common variant form 𦍌. If you go to the entry for 𦍌, you'll notice that it's always used on top of other components inside a character; it's almost like the tail end of 羊 is politely contracting to make room for the other components. It's nice to think of the components this way, as helpful alternative forms that make the characters easier to write.
Just a few variant forms exhibit more dramatic variations in shape, like 水 water and its variant 氵. In such cases, these variants are grouped together because they descend from a single historical form. Most of these extremely simplified variant forms like 氵 appear so often in common kanji that you won't have to put much effort into memorizing them. If you're supplementing your kanji study with real-world Japanese (which you should be doing!), you'll have most of them mastered in no time.
Atomic components vs. composite components
This list includes only those components which can't be broken up easily into distinct, meaningful sub-components. Since they're indivisible, kind of like atoms, I've dubbed them the "atomic" components. I've also made available an exhaustive list of all the atomic and composite components, which number over 1,200.
Disclaimer: personal judgments ahead!
My ultimate goal here was to come up with a system that makes the kanji and their components easy to remember. With that goal in mind, I've tried to compile a list of all those components which can't be broken up easily into distinct, meaningful sub-components. But "broken up easily" and "meaningful" are ultimately subjective criteria.
I think this is fine. There are no perfectly objective criteria for judging whether something is "easy to remember", since everyone's brain works differently. In the end, I've done the same as everyone else who has ever tried to devise a kanji-learning method, and I've used a good measure of personal judgment in making this list.
So, some of these "atomic" components are ultimately "atomic" only because I've decided they're not worth analyzing any further. You could very well break several of them down into smaller components, but I've held off from doing so where it doesn't seem to make the shapes any easier to remember. Still, if you think I've overlooked something, feel free to message me and I'll take your feedback into consideration!
All the atomic components
Here are all the 278 atomic components and their keywords, with any variants grouped together. They are presented in order from the most common to the rarest. For those atomic components that can also serve as sound components, a reading is given in katakana.
blade of grass