Пока неизвестно, кто придёт.

Here пока means for now / so far / at the moment, not while.

So:

• Пока неизвестно = It’s not known yet / So far it’s unknown

This is a very common use of пока in everyday Russian.

Compare:

• Пока неизвестно, кто придёт. = It’s not known yet who will come.
• Пока я работаю, он читает. = While I’m working, he’s reading.

Same word, different meaning depending on context.

Russian usually omits the present-tense form of "to be".

So where English says:

• It is unknown

Russian simply says:

• неизвестно

Literally, the sentence is closer to:

• For now unknown, who will come

but natural English is:

• It is not yet known who will come

This is normal Russian grammar, not an incomplete sentence.

Because неизвестно here is being used impersonally, not as an adjective describing a noun.

In this sentence, there is no noun like the person or the plan that неизвестный would agree with. Instead, неизвестно means something like:

• it is unknown
• it is not known

Compare:

• Его адрес неизвестен. = His address is unknown.

  • Here неизвестен agrees with адрес (masculine singular).

• Пока неизвестно, кто придёт. = It’s not yet known who will come.

  • Here the construction is impersonal, so неизвестно is used.

Because кто придёт is a subordinate clause: who will come.

Russian normally puts a comma between the main clause and a subordinate clause:

• Пока неизвестно, кто придёт.

Structure:

• Пока неизвестно = main clause
• кто придёт = subordinate clause

This is very standard in Russian punctuation.

Because кто is the subject of придёт in the subordinate clause.

In кто придёт:

• кто = who
• придёт = will come

Since who is doing the action, Russian uses the nominative case:

• кто

If it were an object, you might see another case:

• Я не знаю, кого пригласят. = I don’t know who will be invited.

But here the meaning is who will come, so кто is correct.

Because кто is grammatically treated as singular in Russian.

So Russian says:

• Кто придёт? = Who will come?

even if the answer could name several people.

This is similar to English in some contexts: Who is coming? can refer to one person or several people, but the grammar still centers on who as a singular-looking question word.

So:

• кто придёт = grammatically singular
• meaning = may refer to one or more people, depending on context

Придёт is the 3rd person singular future of прийти (to come / to arrive).

A few useful forms:

• прийти = infinitive
• я приду = I will come
• ты придёшь = you will come
• он / она / кто придёт = he / she / who will come

So in this sentence:

• кто придёт = who will come

Because the sentence refers to a future completed arrival, so Russian uses the perfective future.

• прийти is perfective
• придёт = will come / will arrive

If you said приходит, that would normally mean comes / is coming in a present or habitual sense, not this future meaning.

Russian aspect matters here:

• кто придёт = who will come (a future arrival)
• кто приходит = who comes / who is coming regularly (different meaning)

So придёт is the natural choice.

This is an important irregularity to learn.

The infinitive is:

• прийти

But the future forms use the stem прид-:

• приду
• придёшь
• придёт

So although the infinitive has й, that й does not stay in these forms.

Also, the ё is important because it shows the stress:

• придёт

In informal writing, Russians sometimes write придет without the dots, but it is still pronounced придёт.

Yes. Russian word order is flexible.

The given sentence:

• Пока неизвестно, кто придёт.

is the most neutral and natural way to say it.

But you could also say:

• Кто придёт, пока неизвестно.

This puts more focus on who will come.

Both are correct, but they feel slightly different in emphasis:

• Пока неизвестно, кто придёт. = neutral, natural
• Кто придёт, пока неизвестно. = emphasizes the unknown people first

Then the sentence becomes more general and less temporary:

• Неизвестно, кто придёт. = It is unknown who will come.

With пока, the sentence suggests:

• we may find out later
• right now we don’t know yet

So:

• Пока неизвестно = not known yet / for now unknown
• Неизвестно = simply unknown

The version with пока often sounds more natural when the situation is still developing.