Sino-Japanese Readings as Fossils of Chinese Sound History

Core examples: 行: こう/ぎょう/あん, 明: めい/みょう, 音: おん/いん, 漢音, 呉音, 唐音, 仏教, 行政.

The readings are not random; they are historical

A learner sees one kanji with multiple on-readings:

行 こう / ぎょう / あん

明 めい / みょう

音 おん / いん

At first, this looks arbitrary. Why does the same character have more than one Sino-Japanese reading? Why not just one reading per character?

The answer is history. Chinese characters and words entered Japanese through different periods, regions, domains, and traditions. The readings preserved in Japanese are not modern Mandarin. They are Japanese adaptations of older Chinese pronunciations as transmitted through historical contact.

The key principle is:

Sino-Japanese readings are sound fossils: Japanese pronunciations preserving traces of earlier Chinese contact layers.

They are not exact reconstructions of ancient Chinese, but they carry historical layering.

On-yomi is not one thing

音読み

means Sino-Japanese reading. But on-yomi includes several layers. The major traditional categories include:

呉音 Go-on

漢音 Kan-on

唐音 Tō-on

These labels point to different historical channels of borrowing. They often correlate with domains: Buddhist vocabulary, official/classical learning, later borrowings, and specialized terms.

A learner does not need to classify every word at first. But knowing that readings have layers makes irregularity less mysterious.

呉音 and Buddhist vocabulary

Go-on readings are often associated with earlier layers and Buddhist vocabulary.

Example:

行者 ぎょうじゃ ascetic/practitioner

The reading ぎょう for 行 appears in religious and older vocabulary. Many Buddhist terms preserve readings that differ from later official kango patterns.

漢音 and official/classical vocabulary

Kan-on readings are often associated with later official or scholarly borrowings.

Example:

行政 ぎょうせい in modern Japanese, though reading history and domain complexity can vary by word

明治 めいじ

Kan-on became important in official, scholarly, and educated vocabulary.

唐音 and later borrowings

Tō-on refers to later borrowings from Chinese, often in specialized, Zen, trade, or material-culture vocabulary. These readings may feel irregular because they entered later and did not always align with older reading systems.

A common learner takeaway:

If an on-reading seems unusual, it may belong to a different historical layer or lexicalized borrowing.

Modern Mandarin is not the key

Modern Mandarin can sometimes help Chinese-literate learners guess broad correspondences, but it is not a reliable predictor of Japanese on-readings. Both Japanese and Mandarin changed over time. Japanese also preserved multiple borrowed layers.

For example, 明 may be めい in 明治 and みょう in 明王. Mandarin míng is related historically but does not tell you which Japanese reading appears in which compound.

Learner action: learn compounds and reading families, not just character-to-Mandarin mapping.

Reading families are useful

Even if you do not study historical phonology deeply, reading families help.

Example:

明 めい: 明治, 明確, 説明 みょう: 明王, 光明 in some Buddhist contexts

Example:

行 こう: 行動, 銀行 ぎょう: 行列, 行事, 修行 あん: 行脚, historically/specialized

Group readings by compounds and domains.

Example bank walkthrough

行: こう / ぎょう / あん

Multiple reading layers and domains.

Learner action: learn by compound family.

明: めい / みょう

めい common in modern kango; みょう often in Buddhist/older terms.

Learner action: domain helps.

音: おん / いん

Multiple Sino-Japanese reading possibilities.

Learner action: check compound.

漢音

A major on-reading layer.

Learner action: often official/scholarly vocabulary.

呉音

A major on-reading layer.

Learner action: often Buddhist/older vocabulary.

唐音

Later Chinese borrowing layer.

Learner action: expect specialized irregularity.

仏教

Buddhism.

Learner action: important domain for older readings.

行政

Administration.

Learner action: domain vocabulary may preserve specific reading.

On-reading profile workflow

For a kanji with multiple on-readings:

1. List common readings.
2. Attach example compounds to each reading.
3. Mark domain: Buddhist, official, everyday, technical, name, rare.
4. Compare with modern Chinese only cautiously.
5. Learn reading through actual words.
6. Use dictionary labels when available.
7. Do not force one reading across all compounds.

On-readings are historical layers, not Mandarin approximations

Modern Mandarin can sometimes provide a weak memory clue, but it is not a reliable source for Japanese on-readings. Sino-Japanese readings reflect older borrowing layers from different times and regions, filtered through Japanese phonology.

For example, 行 has こう, ぎょう, and あん-related readings in different compounds and domains. These are not arbitrary noise; they are historical residue plus lexical convention.

Compound families as memory anchors

Instead of memorizing on-readings as abstract lists, build compound families.

行政 銀行 修行 行者

Each compound teaches which reading appears in which domain. Buddhist vocabulary, government vocabulary, and everyday compounds may preserve different layers.

Reading-layer humility

Even if you know the likely layer, do not force it. Dictionaries label 呉音, 漢音, 唐音, and other readings because the history is complex. For learners, the practical payoff is not proving the layer; it is remembering that readings entered Japanese through multiple paths.

A useful note format:

Character: 明 Readings: めい, みょう Example compounds: 明治, 明王 Domain feel: modern era name/government versus Buddhist/classical flavor

A strong tool for this article would connect readings to domains.

Suggested functions:

1. Character input: 行, 明, 音.
2. Reading list: go-on, kan-on, tō-on labels where available.
3. Compound examples.
4. Domain color-coding: Buddhist, official, modern, specialized.
5. Mandarin comparison warning.
6. **Audio playback for each reading.
7. Spaced-review export by compound family.

Final rule

Sino-Japanese readings are historical layers, not arbitrary noise.

Japanese borrowed character readings through different channels and periods. That is why one kanji may have several on-readings. Learn the readings through compounds, domains, and historical awareness.

The irregularity is history made audible.