日 (hi): Sun, day 三日 (mitsuka): The 3rd, three days
One character. Four valid readings. All correct, depending entirely on context.
Onyomi vs. Kunyomi: The Short Answer
On’yomi (音読み) is a Sino-Japanese reading associated with the historical pronunciation of a kanji. Kun’yomi (訓読み) is a native Japanese reading associated with the character’s meaning. The practical shortcut is simple: multi-kanji compounds often use on’yomi, while kanji with okurigana usually use kun’yomi. Neither pattern is absolute.
Strong clues
Kanji + kanji compound: try on’yomi first. 電車 (でんしゃ) is a straightforward example.
Kanji + okurigana: try kun’yomi first. 食べる (たべる) uses the kun’yomi of 食.
Weak clues
A word sounding formal or technical often uses on’yomi, but this is not a classification rule.
A single kanji used as a familiar standalone word often uses kun’yomi, but there are exceptions.
What you see
First guess
Example
Two or more kanji
Often on’yomi
電車 (でんしゃ)
Kanji followed by okurigana
Usually kun’yomi
食べる (たべる)
Mixed or irregular word
Learn the vocabulary item
手本 (てほん), 場合 (ばあい)
The useful skill is not memorizing every possible reading. Learn readings inside real words, then use these patterns as predictions when you meet unfamiliar vocabulary.
Why Japanese Has Both Readings
Japanese didn’t originally have a writing system. Spoken Japanese existed long before anyone thought to write it down, and when Chinese characters (漢字, kanji) arrived from China via Korea somewhere around the 5th century CE, the Japanese faced a practical problem: how do you use a foreign writing system for your own completely unrelated language?
Japanese adapted kanji for more than one purpose. A character could be used for its sound, giving rise to readings that became part of on’yomi, while an existing Japanese word could be associated with the character’s meaning, giving rise to kun’yomi. A single kanji can therefore carry both types of reading.
On’yomi: The Import
Chinese characters arrived in waves, via different Chinese dialects at different historical periods. This is why some kanji have multiple on’yomi: an earlier reading borrowed from Middle Chinese and a later one borrowed after the dialect had shifted. The kanji 行 has both kou and gyou as on’yomi for exactly this reason.
Kun’yomi: The Native Layer
Kun’yomi represent the original Japanese language: the words people were already using before writing existed. When a character arrived with a Chinese meaning, someone decided which existing Japanese word it matched and attached it. These readings often feel more “natural” because they’re the words Japanese people had been speaking for generations.
The result is a writing system that carries the weight of two entirely different language families. Every kanji is, in a sense, carrying both its Chinese history and its Japanese history at once. This is why kanji readings feel complicated. They’re not random; they’re the sediment of twelve-plus centuries of linguistic layering.
Before getting into the patterns, it helps to see the difference side by side with a concrete example. Take the kanji 山 (mountain).
Reading Type
Reading
Example Word
Meaning
ON’YOMI
サン (san)
富士山 Fujisan
Mount Fuji
KUN’YOMI
やま (yama)
山 yama
A mountain
ON’YOMI
サン (san)
山頂 sanchō
Mountain summit
KUN’YOMI
やま (yama)
山道 yamamichi
Mountain path
Notice that 山道 (yamamichi) is two kanji both read with kun’yomi, while 山頂 (sanchō) uses on’yomi for both. That pattern is not a coincidence. It’s one of the most reliable rules in the whole system, and we’ll get to it.
Dictionaries typically list on’yomi in katakana (サン) and kun’yomi in hiragana (やま). This convention exists specifically so you can tell them apart at a glance, so once you know this, those dictionary entries become a lot less mysterious.
Why Onyomi Is Written in Katakana
The katakana-for-onyomi convention isn’t random. It goes back to how katakana was used in the first place, and understanding it can actually make onyomi easier to remember instead of just another arbitrary rule to memorize.
A Dictionary Convention
Modern Japanese references commonly distinguish the two categories typographically: on’yomi is shown in katakana and kun’yomi in hiragana. The official Agency for Cultural Affairs on/kun index gives the same convention. This is a notation system for identifying readings, not a rule that Japanese sentences write on’yomi in katakana.
Why the Convention Helps
Once you see サン beside やま in a dictionary or study card, the script itself tells you which reading category you are looking at. In ordinary Japanese text, both readings are normally written with kanji. The katakana/hiragana distinction is mainly useful when readings are being listed or taught.
Using Katakana as a Memory Tool
Once you know why the convention exists, you can use it deliberately instead of just noticing it. A few ways this helps in practice:
Let the script do the sorting for you. If you write or drill a reading in katakana, you’re automatically telling your brain “this is the Chinese-origin one, expect it in compound words.” Writing サン instead of just “san” on a flashcard bakes that category into the visual, not just the sound.
Borrow the loanword association. You likely already have strong pattern recognition for katakana from reading loanwords like テレビ (terebi, TV) or アイス (aisu, ice cream). That same “this is a borrowed sound” instinct transfers directly to onyomi, since it’s a borrowed sound too.
Use the sound shape as a second signal. Some on’yomi readings have forms such as サン, ガク, コク, or ニチ. But kun’yomi can also end in kana such as く or つ, so sound shape is only a weak clue. Use word structure and vocabulary first.
None of this changes how the words are written in real sentences: both onyomi and kunyomi vocabulary is normally written with kanji, not katakana or hiragana alone. But when you’re studying readings in isolation, in a dictionary entry or a flashcard, matching the script to the reading type turns an abstract label into a visual cue your memory can actually grab onto.
For the formal 音/訓 notation used in Japanese kanji references, see the official on/kun index.
Key Terminology
These terms come up constantly in kanji study materials. Worth knowing them before they appear unexpectedly in a textbook footnote.
On’yomi 音読み
The Chinese-derived reading of a kanji character. Borrowed phonetically from Chinese pronunciation, though heavily adapted to fit Japanese sound patterns over time. Usually appears in jukugo (multi-kanji compound words). Shown in katakana in dictionaries.
Kun’yomi 訓読み
The native Japanese reading of a kanji character. Assigned to a character based on meaning: the Japanese word that already existed for that concept. Often accompanied by okurigana. Shown in hiragana in dictionaries.
Jukugo 熟語
A compound word made of two or more kanji. Many jukugo use on’yomi, but mixed and kun’yomi compounds are common enough that this is a prediction, not a rule. Examples: 電車 (densha, train), 図書館 (toshokan, library), 日本語 (nihongo, Japanese language). This is where on’yomi dominates, and knowing this pattern saves a lot of guessing.
Okurigana 送り仮名
Hiragana characters written after a kanji that complete a word, particularly verbs and adjectives. They signal kun’yomi. If you see 食べる, the べる is okurigana; the kanji 食 is read as “ta” (kun’yomi). If you see 飲む, む is okurigana and 飲 is read “no” (kun’yomi).
Nanori 名乗り
Onyomi vs. Kunyomi vs. Nanori
Nanori is a third category of readings, used almost exclusively in Japanese proper names: people’s names and place names. Unlike on’yomi and kun’yomi, nanori readings don’t follow reliable rules, which is why Japanese names are notoriously difficult to pronounce from the characters alone. If you’ve ever been blindsided by a name reading, nanori is the culprit.
Jōyō Kanji 常用漢字
The 2,136 kanji designated by the Japanese government for general use in education and media. Each has an officially listed set of on’yomi and kun’yomi. This list is the standard reference for “how many readings does this kanji have?”, though real usage sometimes goes beyond it.
Core Differences
Beyond where they came from, on’yomi and kun’yomi differ in some observable ways that are actually useful for identification.
Feature
On’yomi
Kun’yomi
Basic origin
Readings connected to historical Chinese pronunciation
Native Japanese readings associated with a character’s meaning
Typical structure
Common in multi-kanji compounds
Common in standalone words and words with okurigana
Dictionary notation
Usually katakana, such as サン
Usually hiragana, such as やま
Okurigana
Usually absent
Common in verbs and adjectives
How reliable is the clue?
Compound structure is useful; individual words can still be exceptions
Okurigana is a strong clue; standalone use is less certain
Sound shape can help a little, but it should not be your main test. Some on’yomi readings have forms such as サン, ガク, コク, or ニチ. Kun’yomi can also end in kana such as く or つ, so endings such as -n or -ku are not reliable signals. Word structure and the vocabulary item itself are better clues.
These patterns help you make a first guess. They are useful shortcuts, not rules that determine every reading.
ON’YOMI When On’yomi Tends to Appear
1. Two or More Kanji Together (Jukugo)
This is the big one. When two or more kanji form a compound, on’yomi is common, especially in Sino-Japanese vocabulary. But mixed readings, kun’yomi compounds, and irregular words also occur. This applies to the vast majority of compound nouns you’ll encounter.
電車 (densha): train | 図書館 (toshokan): library | 東京 (Tōkyō): Tokyo | 日本語 (nihongo): Japanese language | 勉強 (benkyō): study
2. Numbers and Counters
When kanji numbers appear with counters (units of measurement), on’yomi dominates, though there are notable exceptions with 日 (date counters) and 人 (person counter), which have kun’yomi for small numbers.
三冊 (sansatsu): three books | 六時 (rokuji): six o’clock | 百円 (hyakuen): 100 yen
3. Formal and Technical Vocabulary
Formal language, academic terms, and specialized vocabulary tend to be Sino-Japanese compounds and use on’yomi throughout. When you’re reading a newspaper, a legal document, or a medical text, on’yomi is handling most of the heavy lifting.
経済 (keizai): economy | 環境 (kankyō): environment | 医療 (iryō): medical care
KUN’YOMI When Kun’yomi Tends to Appear
1. Kanji Followed by Okurigana
This is the clearest signal in the entire system. When hiragana follow immediately after a kanji as part of the same word (not as a particle, but as the word’s grammatical ending), you’re looking at kun’yomi. Verbs and adjectives work this way almost without exception.
食べる (taberu): to eat | 書く (kaku): to write | 高い (takai): tall, expensive | 見る (miru): to see
2. A Single Kanji Standing Alone as a Word
When a single kanji functions as a complete noun on its own, without combining with other kanji, kun’yomi is the more likely reading. The kanji is being used directly as the native Japanese word for that concept.
木 (ki): tree | 火 (hi): fire | 水 (mizu): water | 空 (sora): sky | 山 (yama): mountain
3. Everyday Conversational Words
When the same concept has both a Sino-Japanese compound form and a native Japanese form, the native form is typically kun’yomi. Words for family members in casual speech, basic actions, and natural phenomena tend to be kun’yomi.
Some compound words mix on’yomi and kun’yomi in a single word. These patterns have traditional names, but you do not need the labels to read the words.
湯桶読み (Yutōyomi)
Kun’yomi first, on’yomi second. The name comes from 湯桶 (yutō), which follows the same pattern.
Examples: 手本 (tehon): te (kun) + hon (on); 夕飯 (yūhan): yū (kun) + han (on).
重箱読み (Jūbakoyomi)
On’yomi first, kun’yomi second. The name comes from 重箱 (jūbako), which follows the same pattern.
Examples: 台所 (daidokoro): dai (on) + dokoro (kun); 番組 (bangumi): ban (on) + gumi (kun).
You don’t need to memorize these terms. They exist mostly to explain why certain common words don’t follow the main patterns. When you encounter one of these words, the only reliable approach is to recognize it as a vocabulary item rather than try to derive it from rules.
Worked Examples
Abstract rules are easier to use once you’ve watched them applied to specific characters. Here are four common kanji walked through both reading types with real-world examples.
山
mountain
ON: サン (san)KUN: やま (yama)
On’yomi in use
富士山 (Fujisan): Mount Fuji
火山 (kazan): volcano
登山 (tozan): mountain climbing
Kun’yomi in use
山 (yama): a mountain
山道 (yamamichi): mountain path
山登り (yamanobori): hiking
人
person, people
ON: ジン / ニン (jin / nin)KUN: ひと (hito)
On’yomi in use
日本人 (nihonjin): Japanese person
人気 (ninki): popularity
外国人 (gaikokujin): foreigner
Kun’yomi in use
人 (hito): a person
一人 (hitori): one person (alone)
二人 (futari): two people
Note: 人 has two on’yomi: jin (for nationalities and standalone compounds) and nin (for counting people and certain compounds like 人気). This split is common with high-frequency kanji and just needs to be learned per-word.
水
water
ON: スイ (sui)KUN: みず (mizu)
On’yomi in use
水曜日 (suiyōbi): Wednesday
水泳 (suiei): swimming
洪水 (kōzui): flood
Kun’yomi in use
水 (mizu): water
お水 (omizu): water (polite)
水色 (mizuiro): light blue (lit. water color)
食
eat, food
ON: ショク / ジキ (shoku / jiki)KUN: た (ta-), く (ku-)
On’yomi in use
食事 (shokuji): a meal
食堂 (shokudō): cafeteria, dining hall
食料 (shokuryō): food supplies
Kun’yomi in use
食べる (taberu): to eat
食べ物 (tabemono): food
食べ放題 (tabehodai): all-you-can-eat
When One Kanji Has Many Readings
Some kanji have been borrowed multiple times from different Chinese dialects at different historical periods, and they’ve picked up multiple on’yomi as a result. Others have multiple kun’yomi because the same character was mapped to several related Japanese words over time. And then there’s 生, which is a useful example because it has several common readings.
生: A Kanji With Many Lives
Multiple on’yomi, multiple kun’yomi, and readings for names you just have to accept
On’yomi
セイ (sei): 先生 (sensei), 学生 (gakusei)
ショウ (shō): 誕生 (tanjō), 一生 (isshō)
Kun’yomi
い (i-): 生きる (ikiru, to live)
う (u-): 生まれる (umareru, to be born)
なま (nama): 生ビール (nama biiru, draft beer)
き (ki-): 生地 (kiji, fabric)
Name readings
お (o), いく (iku), ふ (fu), はる (haru), みき (miki)...
Japanese names using 生 can be read in over a dozen different ways. There is no reliable pattern.
生 is often cited as one of the kanji with the most readings; the exact count depends on which readings, names, and vocabulary conventions are included. Context resolves many of them, but names can require a lookup.
The important takeaway from kanji like 生 is that memorizing all possible readings in the abstract is not the goal. The goal is to learn words. When you know 先生 (sensei), you know that 生 reads as sei in that word. When you know 生ビール (nama biiru), you know 生 reads as nama there. Each word is its own unit. The list of possible readings is reference material, not a study target.
The Compound Context Rule
When you encounter an unfamiliar word that combines a kanji you know with a new kanji, you have some useful information: if both kanji appear without okurigana, try on’yomi for both. You’ll be right a majority of the time. If okurigana appear, use kun’yomi for the kanji they’re attached to. Neither rule is absolute, but both are better than guessing randomly.
How to Actually Learn Them
Knowing the difference between on’yomi and kun’yomi is useful. Here’s how to translate that into an actual study approach.
Learn Words, Not Isolated Readings
The biggest mistake new learners make is trying to memorize every possible reading for each kanji before using them in words. This is the wrong order of operations. Instead, learn vocabulary, real words you’ll encounter in Japanese, and let the readings reveal themselves through repetition. When you know 電車 (densha) and 電話 (denwa), you know that 電 reads as den in compounds. That sticks better than a flashcard listing “電: デン (den), テン (ten).”
This is also why immersive reading matters so much for kanji: encountering a character in multiple real contexts, across multiple sentences, is what actually anchors its readings in memory, not reviewing them in isolation. Reading tools like YoMoo, which pair native articles with furigana and dictionary lookups, are built around exactly this kind of repeated exposure.
Use the Patterns Actively When Reading
The rules aren’t just abstract knowledge; use them as live tools when you encounter unfamiliar text. Before looking up a word, make a prediction: is there okurigana? Then try kun’yomi. Is it a bare compound? Try on’yomi. Check if you were right. This active prediction habit builds pattern recognition faster than passive memorization, and it makes reading practice more cognitively engaging.
Practical workflow: When you see an unfamiliar word in something you’re reading, pause for a second, look at its structure, and guess the reading type before reaching for the dictionary. Even wrong guesses are useful; they highlight exactly where your intuition is miscalibrated.
Group Words by Kanji, Not by Reading Type
When studying a new kanji, learn at least one clear on’yomi example word and one clear kun’yomi example word together. For 山: learn 火山 (kazan, volcano) for on’yomi, and 山道 (yamamichi, mountain path) for kun’yomi. Concrete paired examples do more for reading intuition than abstract reading lists. The contrast makes both readings more memorable.
If you use Anki or another SRS, tag words explicitly with “on” or “kun” rather than leaving the distinction implicit. When you review them, notice which reading type you’re working with. That meta-awareness builds over time. FluencyTool's decks include a per-kanji breakdown with both readings, so this tagging is visible on each card by default.
Accept That Some Words Are Just Exceptions
The patterns described here cover the majority of cases, but they’re not laws of physics. Japanese has centuries of exceptions, irregular readings, and words that simply don’t fit any rule. 今日 (kyō, today) and 今年 (kotoshi, this year) don’t follow standard compound reading patterns. 明日 can be read as ashita or myōnichi depending on formality and context. 一人 (hitori) and 二人 (futari) use irregular kun’yomi that don’t match the standard number+counter pattern.
These aren’t failures of the system; they’re vocabulary items. When you hit one, just learn it as a fixed unit and move on. Fighting every exception is a reliable way to slow yourself down.
Read More Than You Drill
The pattern recognition that makes kanji readings be easier to recognize comes from volume. Reading native Japanese content, even at a level that still requires a lot of lookups, exposes you to the same kanji in dozens of different contexts, building the implicit models that rules alone can’t create. Flashcards and reading are both useful. But if your goal is to read actual Japanese without constantly guessing, reading actual Japanese is a required part of the process, not an optional reward for finishing your Anki reviews.
Frequently Asked Questions
Is on’yomi always used in kanji compounds?
No. On’yomi is common in multi-kanji compounds, but compounds can use kun’yomi, mixed readings, or irregular readings. Treat the structure as a prediction, then learn the actual word.
Does okurigana always mean kun’yomi?
It is one of the strongest practical clues. In words such as 食べる and 書く, the kanji uses kun’yomi and the following hiragana is okurigana. The key is that the hiragana belongs to the word, rather than being a separate particle.
Why does one kanji have multiple readings?
Kanji entered Japanese through a long history of contact with Chinese, and Japanese also attached existing native words to characters by meaning. Individual characters can therefore have multiple on’yomi, multiple kun’yomi, or special readings used in particular words and names.
How can I guess the reading of an unfamiliar kanji word?
First check the structure. For a multi-kanji compound, try on’yomi. For kanji followed by okurigana, try kun’yomi. If the word is mixed, irregular, or a name, make a cautious guess and then check a dictionary.
When should I stop guessing and look it up?
Look it up when the word is unfamiliar, the pattern gives conflicting clues, or the word may be a name or an exception. The goal of the patterns is to make your first guess more informed, not to eliminate dictionary use.
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Conclusion
On’yomi and kun’yomi are useful categories, but Japanese vocabulary is not governed by a single set of reading rules. Use word structure as your first clue: compounds often use on’yomi, while okurigana usually signals kun’yomi.
Then learn the actual vocabulary. Mixed readings, historical spellings, and irregular words are part of normal Japanese, so a dictionary lookup is sometimes the correct answer rather than a failure to apply a rule.
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