In English, "the door opened" and "I opened the door" use the same verb "open." Japanese doesn't work that way. Japanese verbs are divided into two categories: 自動詞 (intransitive, things happen on their own) and 他動詞 (transitive, someone makes it happen). This classification directly determines which particle you use.
What Are 自動詞 and 他動詞?
In simple terms:
- 他動詞 (transitive): Someone performs an action that changes something else. → Object takes を
- 自動詞 (intransitive): Something changes on its own, or a person moves without acting on anything. → Subject takes が
| Transitive (他動詞) | Intransitive (自動詞) | |
|---|---|---|
| Core idea | Someone acts → changes something | Something changes on its own / person moves |
| Particle | Object + を | Subject + が |
| Example | ドアを開ける (open the door) | ドアが開く (the door opens) |
The Big Three Particles: が, を, に
The three most important particles in Japanese are が (subject), を (object), and に (target/recipient). Understanding intransitive and transitive verbs makes these particles click into place.
Two Patterns for Transitive Verbs
Basic pattern: Subject (が) + Object (を) + Transitive verb
弟がラーメンを食べる。 → My brother eats ramen.
Double-object pattern: Subject (が) + Target (に) + Object (を) + Transitive verb
私は先生に質問を聞く。 → I ask the teacher a question.
The subject of transitive verbs is generally a person, since someone needs to perform the action.
Two Patterns for Intransitive Verbs
No-object pattern: Subject (が) + Intransitive verb
ドアが開く。 → The door opens.
雨が降る。 → It rains.
With-object pattern: Subject (が) + Object (に) + Intransitive verb
When intransitive verbs take an object, it uses に instead of を.
Note: The subject of intransitive verbs can be either a person or a thing. But when the subject is a thing (no specific person acting), you almost always use an intransitive verb.
The Golden Rule: Thing as Subject → Intransitive Verb
This is the most practical decision method:
- Thing as subject → use 自動詞 (intransitive)
- Person acting on a thing → use 他動詞 (transitive)
| English | Japanese | Reasoning |
|---|---|---|
| The door is open | ドアが開いている。 | Door (thing) is the subject → intransitive |
| My brother opens the door | 弟がドアを開ける。 | Brother (person) opens door (thing) → transitive |
| Music is playing | 音楽が流れている。 | Music (thing) is the subject → intransitive |
| He plays music | 彼が音楽を流す。 | He (person) plays music (thing) → transitive |
Three Restrictions on Thing-Subject Verbs
This is crucial — if a verb inherently takes a thing as its subject (usually intransitive), there are three things it cannot do:
| Restriction | Reason | Wrong example |
|---|---|---|
| No potential form | Things have no ability | |
| No たい | Things have no desires | |
| No てください | You can't request a thing to do something |
Only verbs with a person as the subject can use the potential form, たい, or てください.
ドアを開けてください。 → Please open the door. (Transitive, person as subject → OK)
ドアを開けたい。 → I want to open the door. (Transitive, person as subject → OK)
ドアを開けられる。 → I can open the door. (Transitive, person as subject → OK)
How Do You Know if a Verb Is Intransitive or Transitive?
Unfortunately, just like English transitive/intransitive verbs — you mostly have to memorize them one by one. But there is one near-universal rule:
| Pattern | Conclusion | Accuracy |
|---|---|---|
| Ends in す | → Transitive (他動詞) | ~99% |
| Ends in まる | → Intransitive (自動詞) | ~99% |
For example: 流す (ながす) → ends in す → transitive; 集まる (あつまる) → ends in まる → intransitive.
When looking up verbs in a dictionary, check for the 「自」or「他」label. If your dictionary app doesn't show this, consider switching to one that does.
Summary
- Transitive = someone acts on something, object takes を; subject is usually a person
- Intransitive = happens on its own, subject takes が; subject can be a person or a thing
- Thing as subject → use intransitive is the most practical rule
- Thing-subject verbs cannot use potential form, たい, or てください
- Ends in す → almost certainly transitive; ends in まる → almost certainly intransitive
Practice Questions
Q1. Fill in the particles: 「ドア＿＿開いている」and「ドア＿＿開ける」
Answer
- ドアが開いている。 (Intransitive 開く → thing as subject → が)
- ドアを開ける。 (Transitive 開ける → thing is the object → を)
Q2. Why does「雨が降りたいです」sound unnatural?
Answer
Because the subject of 降る is 雨 (rain, a thing). Thing-subject verbs cannot take たい. たい expresses inner desire, and things don't have desires.
Q3. 「音楽＿＿流す」and「音楽＿＿流れている」— what particles go in the blanks?
Answer
- 音楽を流す。 (Transitive → object takes を)
- 音楽が流れている。 (Intransitive → subject takes が)