If you have ever been confused about whether to use the particle が (ga) or を (o), this article is for you. We will explain this classic intransitive (自動詞) and transitive (他動詞) pair with simple examples and a quiz.
Usage Explanation ①: 開く (aku) – “Something opens” (Intransitive)
First, let’s look at 開く (aku). This is an **intransitive verb (自動詞 – jidoushi)**.
An intransitive verb describes an action that happens *by itself*. The thing (like a door) is the subject, and it does the action. It does not need an object.
The key particle is が (ga). The pattern is: [Thing] が 開く。
- Example 1:
- ドアが 開く。(Doa ga aku.)
The door opens.
- Example 2:
- エレベーターのドアが 開きました。(Erebētā no doa ga akimasu.)
The elevator doors are opening. (They open automatically.)
- Example 3:
- 窓（まど）が 開いています。(Mado ga aite imasu.)
The window is open. (This is the state.)
Key Point: Use 開く (aku) when you want to say “something is open” or “something opens” without saying *who* did it. The focus is on the *thing* (the door, the window).
Usage Explanation ②: 開ける (akeru) – “To open (something)” (Transitive)
Now, let’s look at 開ける (akeru). This is a **transitive verb (他動詞 – tadoushi)**.
A transitive verb describes an action that a *person* (the subject) does *to* something (the object). It needs an object.
The key particle is を (o). The pattern is: [Person] が [Thing] を 開ける。
- Example 1:
- 私（わたし）が、ドアを 開ける。(Watashi ga, doa o akeru.)
I open the door.
- Example 2:
- 窓（まど）を 開けてください。(Mado o akete kudasai.)
Please open the window.
- Example 3:
- 彼（かれ）は、箱（はこ）を 開けた。(Kare wa, hako o aketa.)
He opened the box.
Key Point: Use 開ける (akeru) when a person (or animal) is doing the action of “opening.” The focus is on the *person* doing the action *to* the thing.
Comparison: 開く (aku) vs 開ける (akeru)
Let’s look at the difference side-by-side.
| Feature | 開く (aku) | 開ける (akeru) |
|---|---|---|
| Pronunciation | a-ku | a-ke-ru |
| Verb Type | Intransitive (自動詞) | Transitive (他動詞) |
| Meaning | “Something opens” | “Someone opens something” |
| Focus | The Thing (Door, Window) | The Person (I, You, He) |
| Key Particle | [Thing] が (ga) | [Thing] を (o) |
| Example Sentence | ドアが 開く。 (The door opens.) |
私（わたし）がドアを 開ける。 (I open the door.) |
Common Mistake Examples
Mistake 1: Asking someone to open a window
- Wrong:
- 窓（まど）が 開けてください。(Mado ga akete kudasai.)
- Correct:
- 窓（まど）を 開けてください。(Mado o akete kudasai.)
- Why?
- You are asking the listener (a person) to do an action *to* the window (the object). You must use the transitive verb 開ける (akeru) and the object particle を (o).
Mistake 2: Describing an automatic door
- Wrong:
- （店（みせ）に入（はい）る時）あ、ドアを 開けた。(A, doa o aketa.)
- Correct:
- （店（みせ）に入（はい）る時）あ、ドアが 開いた。(A, doa ga aita.)
- Why?
- The “wrong” sentence means “Oh, (I/someone) opened the door.” But if it’s an automatic door, it opened *by itself*. The door is the subject. You must use the intransitive verb 開く (aku) and the particle が (ga).
Practice Quiz
Let’s check your understanding! Choose the correct word for ( ).
Q1.
（ノック（knock）が聞（き）こえる）「はい、今（いま）、ドア ________！」
(You hear a knock) “Yes, I’m ________ the door now!”
- を 開けます (o akemasu)
- が 開きます (ga akimasu)
Q2.
「暑（あつ）いですね。窓（まど） ________ もいいですか？」
“It’s hot, isn’t it? May I ________ the window?”
- を 開けて (o akete)
- が 開いて (ga aite)
Q3.
「あぶない！バスのドア ________ よ！」
“Watch out! The bus door ________!”
- を 開ける (o akeru)
- が 開く (ga aku)
Quiz Answers
Q1. (a) を 開けます (o akemasu) – “I will open the door.” You (a person) are doing the action *to* the door (object). (Transitive)
Q2. (a) を 開けて (o akete) – “May I open the window?” You are asking to do the action *to* the window. (Transitive)
Q3. (b) が 開く (ga aku) – “The bus door is opening.” The door is the subject doing the action (by itself). (Intransitive)
Summary: Key Differences
How did you do on the quiz? This rule is very important in Japanese!
- 開く (aku) (Intransitive – 自動詞):
Something opens. The thing is the subject.Particle: が (ga)Example: ドアが 開く。(The door opens.)
- 開ける (akeru) (Transitive – 他動詞):
Someone opens something. A person is the subject.Particle: を (o)Example: 私（わたし）がドアを 開ける。(I open the door.)
When you learn a new verb, it is very helpful to check if it is intransitive (like 開く) or transitive (like 開ける). This will help you choose the correct particle!
Frequently Asked Questions (FAQ)
- Q1: What is the simple difference between 開く (aku) and 開ける (akeru)?
- A1: The simple difference is in the particle and who (or what) is doing the action.
- 開く (aku) is intransitive. The *thing* is the subject. It opens by itself. (ドアが開く – The door opens.)
- 開ける (akeru) is transitive. A *person* is the subject who does the action *to* the thing. (私がドアを開ける – *I* open the door.)
- Q2: What about ‘close’? Is there a pair for that too?
- A2: Yes! It follows the exact same pattern.
- 閉まる (shimaru) is intransitive: ドアが 閉まる。 (The door closes.)
- 閉める (shimeru) is transitive: ドアを 閉める。 (I close the door.)
- Q3: What does ドアが開いている (doa ga aite iru) mean?
- A3: This is the -te iru form of the intransitive verb 開く (aku). It means “The door *is open*” (describing the state). It’s very useful! It just describes the situation. We don’t know *who* opened it. We just know the door is currently in an open state.
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