I am currently preparing for the N3 with the 日本語総まとめ books and one question confuses me:

あ、バス、(a. 行かないと b. 行っちゃった)。

Supposedly, a. is wrong while b. is correct. But doesn't a. sound more reasonable, in the sense of "Ah, the bus, I have to go."?

Also, concerning, 行っちゃった, is it common to use 行く when describing the motion of a vehicle? Wouldn't you rather use 出かける or 出発する?

I am grateful for explanations regarding any of those questions!  

4 Answers 4


This answer extends on a lot of what @Earthliŋ♦ and @T.Allred have already posted.

Short answer

The presence of one noun and one verb, in the absence of explicit particles, may imply that the noun is the subject and the verb belongs to that subject. Or, it may imply that the noun is the object of the verb. Given that, it comes down to which answer makes sense logically.

Long answer

a. あ、バス、行かないと。

This may imply


Logically, however, this doesn't make a lot of sense because it means, "Oh, the bus, it has to go".

Or, it may imply


This doesn't make sense, either. It might mean "Oh, we have to walk down the bus".

As @T.Allred explained, 「あ、バスだ。行かないと。」would make this answer correct.

For the second choice,

b. あ、バス、行っちゃった。

Here, one noun, one verb, so again it's implied that the noun can be the subject or object of the verb. Of the two cases, it makes logical sense for the noun to be the subject, so this option is correct. This means, "Aw man, the bus left".

Response to additional question

Also, concerning, 行っちゃった, is it common to use 行く when describing the motion of a vehicle? Wouldn't you rather use 出かける or 出発する?

Yes, it is common to use 行く when expressing that a car, train, etc., has gone, especially when you don't want it to have already gone (行ってしまいました/行っちゃった).

The subject of 出かける is normally a person/people, and, per Earthliŋ♦, it means "to go out". So, although バスが出かける may be grammatically correct, from a logical standpoint it might be a little funny.

出発する literally means "to depart". Usage of 出発する, however, is common from a vehicle operator (driver/pilot) to passengers in the vehicle. It's also common when talking about vehicles with respect to its schedule. In the case of the question, 「あ、バス、出発しちゃった」isn't incorrect. However, あ、○○ ~ちゃった implies that the speaker is talking/thinking to him/herself, or the speaker is talking to a close friend in a colloquial manner. In such a colloquial situation, as @Earthliŋ♦ indicated, 出発する doesn't seem natural, much like, "Aw man, the bus departed" doesn't seem natural, either.

  • In such a colloquial situation, 出発する doesn't seem natural -- 「出る」なら口語的だからいいはずですよね。「あ、バス(が)出ちゃった。」「あ、バス(が)行っちゃった。」の違いは?
    – chocolate
    May 16, 2018 at 2:16
  • 確かに、「出る」でも使えますよね。ただ、「バスが行っちゃった」のほうは「おいていかれた感」が強いと感じますね。「バスが出ちゃった」は、「出てしまったが、次がもうすぐ来るよ」というニュアンスが入っていてると思います。 May 16, 2018 at 18:14

Yes, the 行かないと is saying "I have to go" but evidently that is not what the question wanted to express. The 行っちゃった is saying that that it went (with a feeling of regret or disappointment).

Ah, the bus, it left

行く is a general purpose "go" but 出かける or 出発する would be a more specific "depart".

It would be hard to answer that question without more context but if the sentence were to be "Ah, the bus, I gotta go." I feel it would be more natural to say:



In both sentences

(a) あ、バス、行かないと

(b) あ、バス、行っちゃった

the particle after バス has been omitted. But particles which may be omitted are usually either が or を. (Notice that these are the particles that are usually omitted in combination with は, in contrast to に+は = には, で+は=では, etc.)

In the first sentence neither が nor を makes sense. In the second sentence バスが does make sense.

"Oh, the bus left" is a natural translation for (b). (Of course 行く can mean "to go", but it can also mean "to leave [the place from which you're going]".)

As @T.Allred says, "Ah, the bus, I have to go" would be

あ、バスだ。行かないと (two sentences)

出かける is more like "to go out" (shopping, for a drink, with friends, etc.) and 出発する is quite a stiff word for "to depart".


I think this question is not good because both the sentences make sense.

As answered, "あ、バス、行かないと" can mean "Ah, the bus, I have to go.", this sentence can be used when you talk with someone and the bus comes to you. "あ、バス、行っちゃった" means "Ah, the bus, it left(has gone)".

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