Мне неизвестно, где он живёт.

Because the Russian structure is literally closer to To me, it is unknown where he lives.

• мне is the dative case of я
• Russian often uses impersonal patterns like this to express things such as:
  • Мне холодно = I am cold / literally To me, it is cold
  • Мне интересно = I am interested / literally To me, it is interesting
  • Мне неизвестно = It is unknown to me

So мне is not the subject. It marks the person to whom the state applies.

Here неизвестно functions as a predicative word: something like unknown or not known in an impersonal sentence.

A useful way to understand it is:

• известный = known, famous
• неизвестный = unknown
• неизвестно = it is unknown / unknown

In this sentence, неизвестно does not agree with a noun. It works as the main predicate of the whole clause:

• Мне неизвестно = It is unknown to me

So this is not the same as using a normal adjective before a noun, like:

• неизвестный человек = an unknown person

Because неизвестно is usually treated as a single lexical item meaning unknown.

Compare:

• Мне неизвестно, где он живёт. = It is unknown to me where he lives.
• Это не известно всем. can sometimes be written separately if the meaning is more like not known in a contrastive sense, though in many everyday cases learners should expect неизвестно as one word.

For your sentence, мне неизвестно is the standard spelling.

Yes, in a sense.

Russian often leaves out the present-tense form of to be (есть) in ordinary sentences. So where English says:

• It is unknown to me

Russian simply says:

• Мне неизвестно

There is no need to add a word for is in the present tense.

Also, Russian often does not need a dummy subject like English it. English needs it is unknown; Russian can just say неизвестно.

Because где он живёт is a subordinate clause.

The sentence has two parts:

• Мне неизвестно
• где он живёт

In Russian, subordinate clauses are normally separated by a comma, including indirect questions like this one.

So:

• Мне неизвестно, где он живёт.

The comma is required.

It is an indirect question, not a direct one.

Direct question:

• Где он живёт? = Where does he live?

Indirect question inside a larger sentence:

• Мне неизвестно, где он живёт. = I don’t know where he lives.

Russian keeps normal statement word order in indirect questions. There is no English-style does and no subject-verb inversion.

Yes, absolutely. In fact, that is often the more common and neutral way to say it.

Compare:

• Я не знаю, где он живёт. = I don’t know where he lives.
• Мне неизвестно, где он живёт. = It is unknown to me where he lives.

The second version sounds a bit more formal, detached, or bookish. It can also sound slightly less personal.

So both are correct, but they are not identical in tone.

Yes, it sounds somewhat more formal or official than Я не знаю, где он живёт.

You might hear мне неизвестно in:

• formal speech
• written language
• official or bureaucratic style
• careful narration

In casual conversation, many speakers would more naturally say:

• Я не знаю, где он живёт.
• Не знаю, где он живёт.

So your sentence is correct, but not the most colloquial choice.

Мне is the dative singular form of я.

The dative is used because Russian treats this pattern as a state applying to someone:

• мне = to me
• тебе = to you
• ему = to him
• ей = to her

Examples:

• Мне понятно. = It is clear to me.
• Ему интересно. = It is interesting to him.
• Нам неизвестно. = It is unknown to us.

So the dative is required by this construction.

Because the subordinate clause states a general present fact: where he lives.

• он живёт = he lives / he is living

In Russian, the present tense of an imperfective verb often covers both the general present and ongoing present, depending on context.

Here it means where he lives in the ordinary sense of residence.

Because the verb is жить and the 3rd person singular form is живёт.

• я живу
• ты живёшь
• он/она живёт

In printed Russian, ё is often replaced by е, so you may also see:

• Мне неизвестно, где он живет.

That is common in real texts, but the pronunciation is still живёт, with stress on the last syllable.

Yes, to some extent.

The neutral order is:

• Мне неизвестно, где он живёт.

But Russian word order is flexible, so you could also say:

• Где он живёт, мне неизвестно.

This version puts more focus on where he lives.

Still, the original order is the most straightforward and natural in many contexts.

Yes, that is a very useful literal translation for understanding the grammar.

A natural English translation would usually be:

• I don’t know where he lives.
• It’s unknown to me where he lives.

But as a learner, the literal version helps you see the structure:

• Мне = to me
• неизвестно = unknown / it is unknown
• где он живёт = where he lives

So the literal translation is good for grammar, even if it sounds stiff in normal English.

Yes. This pattern is very productive.

For example:

• Мне неизвестно, кто это сделал. = I don’t know who did it.
• Мне неизвестно, когда он придёт. = I don’t know when he will come.
• Мне неизвестно, почему она ушла. = I don’t know why she left.

So once you understand мне неизвестно, you can use it with many indirect-question clauses.