Meg tudja mondani, mikor indul a vonat?

Meg is a verbal prefix. With mondani, it creates megmondani, which means something like to tell, to say clearly, or to give the information.

In this sentence, meg tudja mondani is an idiomatic pattern meaning can you tell... or are you able to say....

A useful thing to notice is that when a verb with a prefix goes with tud + infinitive, the prefix often appears before tud:

• megmondani = to tell
• meg tudja mondani = can tell

So this is not three separate ideas in English-style word order; it is basically the split form of megmondani.

Because Hungarian is using the definite conjugation here.

The thing being told is a specific piece of information, expressed by the clause mikor indul a vonat. You can think of an understood azt = that:

• Meg tudja mondani (azt), mikor indul a vonat?

That is why tudja is natural here.

So:

• tud = indefinite form
• tudja = definite form

In sentences like this, where the speaker is asking for a specific answer, the definite form is very common.

Because tud normally combines with an infinitive.

This is the standard Hungarian pattern for can / be able to:

• tud + infinitive

So:

• tud beszélni = can speak
• tud jönni = can come
• tudja mondani = can tell

Literally, meg tudja mondani is something like is able to tell it.

It is formal / polite.

The verb form tudja shows that the speaker is addressing someone as Ön, even though Ön is not actually said.

In Hungarian, formal you takes third-person verb forms:

• Ön meg tudja mondani...? = formal
• Te meg tudod mondani...? = informal

So the sentence as written is the kind of thing you would say to a stranger, a clerk, a station employee, or anyone you want to address politely.

Because formal Hungarian works that way.

The formal pronouns Ön and maga behave grammatically like third person, even though they mean you.

So:

• Ön tudja = you know / you can tell (formal)
• Te tudod = you know / you can tell (informal)

This often feels strange to English speakers at first, but it is completely normal in Hungarian.

Hungarian often leaves that out when it is obvious from the situation.

So:

• Meg tudja mondani, mikor indul a vonat?
  already naturally means
  Can you tell me when the train leaves?

If you want to make me explicit, you can add nekem:

• Meg tudja nekem mondani, mikor indul a vonat?

But in many everyday situations, nekem is unnecessary.

Because mikor introduces an indirect question here.

The clause mikor indul a vonat means when the train leaves / when the train departs? as an embedded question.

Compare:

• Mikor indul a vonat? = When does the train leave?
• Meg tudja mondani, mikor indul a vonat? = Can you tell me when the train leaves?

By contrast, amikor usually means when in the sense of at the time when:

• Amikor a vonat indul, mindig sietek. = When the train leaves, I always hurry.

So here mikor is the right choice.

Because Hungarian does not need hogy before an indirect question word.

So this is perfectly normal:

• Meg tudja mondani, mikor indul a vonat?

You may also hear:

• Meg tudja mondani, hogy mikor indul a vonat?

That version is also possible, but hogy is not required. Without it, the sentence is clean and very natural.

Because in Hungarian, a question word such as mikor usually stands directly before the verb.

So the pattern is:

• mikor + verb + subject

That gives:

• mikor indul a vonat

This is true both in direct questions and in embedded questions like this one.

For English speakers, it may help to think of mikor as taking the main focus position, and the verb comes right after it.

Because Hungarian normally uses the definite article when talking about a specific, identifiable thing.

Here, a vonat means the train. Even if the exact train has not been named, the context makes it identifiable: the train being asked about.

So:

• vonat = train
• a vonat = the train

Without the article, the sentence would sound unnatural here.

Yes.

• Meg tudja mondani...? = polite, normal
• Meg tudná mondani...? = even more polite, softer

The second one uses the conditional, which often makes requests sound less direct in Hungarian, just like Could you tell me...? is softer than Can you tell me...? in English.

So both are good, but meg tudná mondani is especially useful in very polite situations.