About
This page explains what Zairyou is, how it works, and how the language data was prepared.
Zairyou
Zairyou (材料) is a free and open-source Japanese language-learning tool. It exists to provide an open, accurate, convenient, user-customizable learning experience for various elements of Japanese. Users can start learning anything from the curriculum at any time and skip content they are already familiar with.
User Data
Zairyou runs entirely on your device, meaning that with the exception of downloading the required site content, your learning progress is stored entirely on your device and nowhere else. There are no user accounts, no subscriptions or paywalls, no remote servers with your data. You have full control of and responsibility for your user data. It is important that you understand how to save and synchronize your data (including across devices). For more on this, see the section on synchronization.
Curriculum
Kanji
Zairyou features the complete set of jouyou kanji (常用漢字), the subset of kanji the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) requires all students in the Japanese school system to learn. The latest revision of the jouyou kanji is from 2010 and features 2,136 characters. MEXT specifies the jouyou kanji here, in particular the characters, Japanese readings, and example words each kanji appears in. Notably, MEXT does not define the meaning of individual kanji.
Zairyou extracts jouyou kanji information from kanjidic2 by filtering all kanji for those that have a grade assigned. Note that middle school is represented as grade 8. Zairyou extracts kanji stroke diagrams from KanjiVG.
The first 1,026 kanji are called the kyouiku kanji (教育漢字) and are taught in elementary school. The remaining kanji are taught in middle school. For the kyouiku kanji, MEXT provides an official table showing which kanji are taught in which grade. Note that elementary school in Japan has 6 grades. The grade grouping for the portion taught in middle school is determined by textbook authors. Note that middle school in Japan has 3 grades.
Zairyou divides the jouyou kanji into 12 groups. The first 6 groups correspond exactly to the sets of kanji taught in grades 1-6. The remaining 1,110 kanji are conveniently evenly divisible by 6, so Zairyou splits the subset taught in middle school into 6 groups as well to keep the number of kanji per group as similar as possible. Zairyou calls the elementary school groups e1, e2, ..., e6 and the middle school groups m1, m2, ..., m6.
There is no official ordering of kanji in each grade. Zairyou orders kanji in its groups by frequency, from more frequent to less frequent. With the exception of a subset of kanji in the final group, m6, all kanji feature a frequency score. Kanji in m6 without a frequency score come after the kanji with a frequency score and are ordered arbitrarily. A kanji's frequency score is extracted as-is from kanjidic2.
Radicals
Zairyou uses a subset of the de facto standard 214 Kangxi radicals used to categorize modern Chinese and Japanese characters. Zairyou modifies the radicals slightly by replacing some traditional characters with their modern Japanese equivalents, updating some readings to forms that are more familiar to modern Japanese speakers, and entirely ignoring radicals that are not the root for any kanji in the jouyou set (爿, 瓜, 禸, 韭, 鬥, 鬲, 鹵, 黍, 黹, 黽, 鼎, 鼠, 齊, 龍, 龜, 龠). Information is taken from various online kanji dictionaries.
Note that there are no official meanings or readings for these radicals, so you will encounter a variety of definitions elsewhere. For some radicals, Japanese people use colloquial names over historically-accurate ones. This is typically done in two ways. The first is a "looks like" description; for example, "⺈" may be described as, "the thing that looks like katakana ク" (カタカナの「ク」みたいなやつ). The second is a "kanji part" description; for example 「発」の上の部分 ("the top part of hatsu").
It is very rare for the typical Japanese speaker to know the names of most of the radicals. Keep in mind that radicals are primarily used to categorize kanji, although they are also useful at times to build mnemonics or grok kanji readings. Use radicals to your advantage when helpful, but do not obsess over them. Note that the 10 most common radicals used as roots in the jouyou kanji (水, 人, 手, 木, 心, 口, 言, 糸, 辵, 土) appear in 779 of the kanji, 35% of the entire set. Also note that over 30 Kangxi radicals occur as a root in only 1 of the jouyou kanji and roughly half of the radicals occur as root less than 10 times each. So, if you are determined to learn the radicals as well, it is probably easiest to learn them as you learn the kanji they appear in.