直る and 治る are both read naoru. 直す and 治す are both read naosu. Same sound, four different words — and English speakers use just two: “fix” and “heal.” This complete guide covers all four verbs in one place: how to choose the right kanji, the transitive/intransitive split, common mistakes, and exactly which particle signals which verb.
YukaI keep writing the wrong kanji for naoru and naosu — sometimes I just write it in hiragana to avoid choosing! Is that okay?
ReiUsing hiragana is fine in casual writing, but in formal contexts the kanji matters. Once you learn the simple rule — 直 for things, 治 for bodies — you will never need to guess again.
At a Glance: All Four Verbs
| Kanji | Reading | Type | Core meaning | Subject/Object |
|---|---|---|---|---|
| 直る | naoru | Intransitive | To get fixed / be corrected | Subject: things, machines, habits, errors |
| 治る | naoru | Intransitive | To heal / to recover | Subject: person, body, illness, wound |
| 直す | naosu | Transitive | To fix / repair / correct | Object (を): things, machines, habits, text |
| 治す | naosu | Transitive | To cure / heal (something) | Object (を): illness, wound, injury |
The Kanji Key: 直 vs 治
The single most important thing to remember about this whole family:
| Kanji | Core meaning | Use for | Memory hook |
|---|---|---|---|
| 直 | Straight / correct / upright | Objects, machines, habits, errors, text, posture | Think: “straighten out” a thing |
| 治 | Govern / cure / heal | Illness, injury, wounds, medical conditions | Think: “treatment” — like a doctor treats you |
Once you have these two kanji anchored, every naoru/naosu question becomes easy: is this about a thing or a body/illness? Thing → 直. Body → 治.
YukaThat is so much simpler than I expected! So if I am talking about my phone breaking, I always use 直, and if I am sick, I use 治?
ReiExactly. And that rule applies to both the intransitive (る-ending) and transitive (す-ending) forms.
直る (Naoru) — A Thing Gets Fixed
直る is intransitive: the broken or incorrect thing is the subject (marked with が or は), and no one is explicitly doing the fixing. Something just gets corrected, repaired, or returns to a proper state.
What can be the subject of 直る?
Machines (パソコン, テレビ, 車), habits (癒), mistakes (間違い), text (文章), posture (姿勢), plumbing, anything non-living that is broken or wrong.
Example 1 — device repaired:
パソコンが直った！
Pasokon ga naotta!
My computer got fixed! (It was sent for repair and came back working.)
Example 2 — household item:
やっとエアコンが直った。
Yatto eakon ga naotta.
The air conditioner finally got fixed.
Example 3 — bad habit:
悪い癒がなかなか直らない。
Warui kuse ga nakanaka naoranai.
My bad habit just won’t go away.
Example 4 — text error corrected:
文章の誤りが直った。
Bunshou no ayamari ga naotta.
The error in the text was corrected.
治る (Naoru) — A Person Heals or Recovers
治る is also intransitive, but the subject is a person, a body part, an illness, or a wound. The body heals itself; a condition clears up on its own.
What can be the subject of 治る?
風邪 (cold), 熱 (fever), 病気 (illness), 恕 (wound), 怀我 (injury), アレルギー (allergy), ニキビ (pimple) — anything relating to the body or health.
Example 1 — cold:
風邪が治った。
Kaze ga naotta.
My cold got better. (lit. The cold healed.)
Example 2 — wound:
恕がきれいに治った。
Kizu ga kirei ni naotta.
The wound healed cleanly.
Example 3 — looking forward to recovery:
もうすぐ治ると思う。
Mou sugu naoru to omou.
I think I’ll recover soon.
Example 4 — chronic condition:
その病気は治らないの？
Sono byouki wa naoranai no?
Won’t that illness get better? / Is there no cure for it?
YukaSo both 直る and 治る use が as the particle? And neither of them needs a person doing the action?
ReiRight — both are intransitive, so the thing being fixed or the illness being healed is the subject. No person doing the fixing is stated. That changes when we get to the す forms.
直す (Naosu) — Someone Fixes or Corrects a Thing
直す is the transitive version of 直る. A person actively repairs, corrects, or improves a thing. The object is marked with を.
Example 1 — repairing a device:
自分でパソコンを直した。
Jibun de pasokon wo naoshita.
I fixed the computer myself.
Example 2 — correcting text:
文章の間違いを直してください。
Bunshou no machigai wo naoshite kudasai.
Please correct the mistakes in the text.
Example 3 — fixing a bad habit:
悪い癒を直そうと努力している。
Warui kuse wo naosou to doryoku shite iru.
I am working to fix my bad habit.
Example 4 — rewrite/redo:
もう一度書き直してください。
Mou ichido kaki-naoshite kudasai.
Please rewrite it one more time. (書き直す = to rewrite; compound verb)
治す (Naosu) — Someone Cures or Heals an Illness/Injury
治す is the transitive version of 治る. A doctor, medicine, or the person themselves actively works to treat an illness or injury. The illness/injury is marked with を.
Example 1 — get well soon:
早く風邪を治してね。
Hayaku kaze wo naoshite ne.
Get well soon! (lit. Cure your cold quickly.) — a very common casual expression
Example 2 — doctor cures:
先生が病気を治した。
Sensei ga byouki wo naoshita.
The doctor cured the illness.
Example 3 — rehabilitation:
怕我を治すためにリハビリをしている。
Kega wo naosu tame ni rihabiri wo shite iru.
I am doing rehabilitation to heal my injury.
Example 4 — treating yourself:
自分で偉を治そうとした。
Jibun de kizu wo naosou to shita.
I tried to heal the wound myself.
YukaSo 直す and 治す use を because someone is doing the action to something? That is the transitive marker?
ReiExactly. を marks the direct object — the thing being fixed or healed. The subject is the person doing the action. Compare: 風邪が治った (the cold healed by itself) vs 風邪を治す (you actively treat your cold).
The Full Four-Way Comparison
| Situation | Intransitive — happens on its own | Transitive — someone does it |
|---|---|---|
| PC breaks / is repaired | パソコンが直った (the PC got fixed) | パソコンを直した (I fixed the PC) |
| Text error / correction | 文章が直った (error was corrected) | 文章を直す (correct the text) |
| Bad habit | 癒が直らない (habit won’t go away) | 癒を直す (fix the habit) |
| Cold / illness | 風邪が治った (cold got better) | 風邪を治す (treat the cold) |
| Wound / injury | 恕が治った (wound healed) | 恕を治す (treat the wound) |
| Fever | 熱が治った (fever broke) | 熱を治す (reduce the fever) |
Common Mistakes to Avoid
Mistake 1 — using 直る for illness:
❌ 風邪が直った。
✅ 風邪が治った。
A cold is a medical condition — always 治.
Mistake 2 — using 治る for a broken machine:
❌ パソコンが治った。
✅ パソコンが直った。
A computer is a thing, not a body — always 直.
Mistake 3 — using 直す for curing illness:
❌ 風邪を直す。
✅ 風邪を治す。
Even in the transitive form, illness uses 治す.
Tricky case — posture and appearance:
姿勢を直す — to fix / correct your posture (直, not 治, because posture is about body position/alignment, not illness or injury)
ReiOne tip: if you’re unsure about the kanji, writing in hiragana is acceptable in casual messages. But for formal writing — and for JLPT — you need to choose correctly.
YukaWhat about compound verbs like 書き直す (rewrite) or 言い直す (rephrase)? They all use 直?
ReiYes! Compound verbs with 直す in the second position (X直す) always use 直 because they mean “redo/redo correctly” — not anything medical. Common ones: 書き直す (rewrite), 言い直す (rephrase), やり直す (redo).
Decision Flowchart: Which Verb?
Is the subject/object a BODY or MEDICAL condition?
(illness, fever, wound, injury, allergy)
|
YES -> use 治 (chi) kanji
| |
| Subject = it/illness -> 治る (naoru) intransitive
| Object = を -> 治す (naosu) transitive
|
NO -> use 直 (nao) kanji
|
Subject = it/thing -> 直る (naoru) intransitive
Object = を -> 直す (naosu) transitive
Quick checks:
"My cold got better" -> 風邪が治った (illness, intransitive)
"Get well soon" -> 風邪を治して (illness, transitive)
"The PC got fixed" -> PCが直った (thing, intransitive)
"I fixed the PC" -> PCを直した (thing, transitive)
"Please correct this" -> これを直して (error/text, transitive)
"The bad habit won't go away" -> 癖が直らない (habit, intransitive)Natural Conversation Examples
Yukaスマホ、また壊れたの？ — Did your phone break again?
Reiうん。でも修理に出したら直ったよ。 — Yeah. But I sent it for repair and it got fixed. (直る — thing was repaired)
Yukaそれは良かった！そういえば、風邪は治った？ — Good to hear! By the way, did your cold get better?
Reiうん、やっと治った。もう元気だよ。 — Yeah, it finally healed. I’m all better now. (治る — illness healed)
Quick Quiz — Test Yourself!
Choose the correct verb (直る/治る/直す/治す) for each blank.
Q1. The broken door finally got fixed.
壊れていたドアがやっと＿＿。
Answer: 直った
Reason: A door is a thing — 直. It fixed itself (intransitive) — 直る.
Q2. It took two months for the broken leg to heal.
折れた足が＿＿のに2か月かかった。
Answer: 治る
Reason: A leg/bone is a body part — 治. Healed on its own (intransitive) — 治る.
Q3. Please correct the mistakes in my essay.
作文の間違いを＿＿てください。
Answer: 直し
Reason: Mistakes are errors (things) — 直. You actively correct them (transitive) — 直す.
Q4. I’m taking medicine to cure my cold.
風邪を＿＿ために薬を飲んでいる。
Answer: 治す
Reason: Cold = illness — 治. You (+ medicine) actively treat it (transitive) — 治す.
Q5. I rewrote the report three times.
レポートを3回書き＿＿。
Answer: 直した
Reason: 書き直す = to rewrite. Report is a thing — 直す.
Frequently Asked Questions
What is the difference between naoru and naosu in Japanese?
Naoru (なおる) is intransitive — something fixes itself or heals on its own. Naosu (なおす) is transitive — someone actively fixes or heals something. Both are written with two possible kanji depending on the context: 直 for things/objects/habits, and 治 for illness/injury/body.
How do I know which kanji to use — 直 or 治?
Use 直 (nao-) when the subject or object is a thing, machine, habit, error, or text. Use 治 (nao-) when the subject or object is a body, illness, wound, or injury. The key question: is this about a medical/body situation? If yes, use 治. If no, use 直.
What does 早く治してね (hayaku naoshite ne) mean?
早く治してね means ‘Get well soon’ (literally: cure your cold/illness quickly). It uses 治す (transitive) because it implies you should actively take care of yourself to recover. This is one of the most common expressions you will hear when someone is sick in Japan.
Can I use hiragana (なおる / なおす) to avoid choosing the wrong kanji?
In casual writing (texts, messages), writing in hiragana is accepted. However, for formal writing, JLPT exams, or business communication, you should use the correct kanji. 直る/直す for things; 治る/治す for medical situations.
What are examples of compound verbs using 直す?
Many compound verbs use 直す in the second position to mean ‘redo’ or ‘redo correctly’: 書き直す (rewrite), 言い直す (rephrase), やり直す (redo), 作り直す (remake), 読み直す (reread). All of these use 直 because they describe redoing an action, not anything medical.
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More transitive/intransitive verb pair guides:
