How to Guess the Reading of a Kanji You Have Never Seen
晴, 清, 精 and 静 mean different things but share the on'yomi セイ, and all four contain 青, which is also read セイ. Many kanji carry a part like this that hints at the sound. Below is how to use it, and the cases where it points you the wrong way.
Two Halves of a Kanji
Most kanji are what Japanese calls 形声文字 (keisei moji): one part hints at the meaning, the other at the sound. In 晴 the sun 日 says “weather”, and 青 says “pronounce me セイ”. In 清 the water radical 氵 says “clear water”, and 青 again gives セイ.
Estimates usually put these at around eight in ten kanji. The sound part is called the 音符 (onpu). It points to the on'yomi only, the reading borrowed from Chinese, so it helps most with compound words, which is where you meet unfamiliar kanji on the JLPT reading paper.
Three Steps to a Guess
- 1
Cover the radical.
The radical is usually on the left (氵, 扌, 言, 木) or on top (艹, 竹). Hide it and look at what is left. In 銅, hiding 金 leaves 同.
- 2
Ask whether you know that part as a kanji.
同 is ドウ, so 銅 is probably ドウ. It is: 銅 (ドウ), copper, as in 銅メダル.
- 3
Treat the answer as a guess and check it.
In a test, use it to rule out options whose sound is far away. In study, look the word up and see whether the guess held. Each time it does, the family becomes easier to recall.
Sound Families to Start With
Each family starts from a kanji you meet between N5 and N3; some members are higher level. Where a family has a member that reads differently, it is listed on the right so you do not learn the rule too strictly.
| Part | On'yomi | Kanji that share it | Careful |
|---|---|---|---|
| 青 | セイ | 晴 清 精 静 請 | |
| 交 | コウ | 校 効 郊 | |
| 反 | ハン | 坂 板 飯 販 | 返 is ヘン |
| 工 | コウ | 功 紅 江 攻 | |
| 白 | ハク | 泊 拍 | |
| 同 | ドウ | 銅 胴 | |
| 化 | カ | 花 貨 | |
| 古 | コ | 固 個 湖 | 苦 is ク |
| 方 | ホウ | 放 訪 芳 | 防 and 房 are ボウ |
| 主 | シュ | 注 柱 駐 (チュウ) · 住 (ジュウ) | the vowel stays, the consonant shifts |
| 寺 | ジ | 時 持 侍 | 待 is タイ, 特 is トク, 詩 is シ |
When the Guess Fails
The sounds behind these families were set in Chinese a very long time ago, and both Chinese and Japanese have changed since. So expect three kinds of miss.
- A voiced version. 方 is ホウ, 防 is ボウ. The guess is one dakuten away, which is often enough to pick the right answer.
- A related sound. 主 is シュ, while 注 and 柱 are チュウ and 住 is ジュウ. The family resemblance is still there if you listen for it.
- A different reading altogether. 毎 is マイ, but 海 is カイ. 寺 is ジ, but 待 is タイ. Here the shared part tells you nothing, and the word has to be learned as it is.
There is a second trap: the part you cover may not be a radical at all. In 好, neither 女 nor 子 gives the sound; it is a meaning-only kanji. If neither half reads like the whole, stop guessing.
For Vietnamese speakers
Sino-Vietnamese readings come from the same Chinese sounds, so the families often line up in your language too: 青 thanh, 清 thanh, 晴 tình, 精 tinh, 静 tĩnh. If you know the Hán Việt reading, you have a second way to recognise the family.
Two Questions That Come Up
Does the sound component work for kun'yomi?
No. The component carries the old Chinese pronunciation, so it only helps with on'yomi. 晴 is セイ in 快晴, but on its own it is read はれる, and nothing in the shape tells you that.
How reliable is guessing from the component?
It is a useful first guess and needs checking. Most kanji are built this way, but sounds have changed over two thousand years, so many families have members that drifted. Use the guess to narrow the options, then check.
See the families as you study
Nihongo Pass shows each kanji with its readings and example words, and brings it back for review just before you would forget it.