Получатель письма ещё не ответил.

Получатель means recipient or receiver. In this sentence, it means the person who received the letter or the addressee.

It comes from the verb получать / получить = to receive.

So:

• получатель = recipient
• письма = of the letter

Together, получатель письма means the recipient of the letter.

Because письма is in the genitive singular.

The basic form is:

• письмо = letter

But after a noun like получатель (recipient), Russian often uses another noun in the genitive to show of:

• получатель письма = recipient of the letter

This is a very common pattern in Russian:

• автор книги = author of the book
• директор школы = director of the school
• получатель письма = recipient of the letter

Russian has no articles, so there is no direct equivalent of the or a/an.

Whether something is understood as the recipient, a recipient, or just recipient depends on context.

So:

• Получатель письма ещё не ответил can mean The recipient of the letter has not replied yet
• In another context, it could also be understood more generally

Usually the surrounding context makes it clear.

Ещё не means not yet.

This is a very common Russian combination:

• ещё = still / yet
• не = not

Together in this kind of sentence:

• ещё не ответил = has not replied yet

More examples:

• Я ещё не ел. = I haven’t eaten yet.
• Она ещё не пришла. = She hasn’t arrived yet.

So in your sentence, ещё adds the idea that a reply may still come later.

Ответил is the past tense masculine singular form.

In Russian, past tense verbs agree in gender and number with the subject:

• ответил = masculine singular
• ответила = feminine singular
• ответило = neuter singular
• ответили = plural

The subject here is получатель, which is a masculine noun, so the verb is:

• получатель ... ответил

Even if the actual person might be female in real life, the grammatical noun получатель is masculine, so the verb normally agrees with the noun.

Russian often uses the past tense where English uses the present perfect.

So:

• ещё не ответил literally looks like did not reply yet
• but in natural English it usually means has not replied yet

Russian does not have a tense that matches the English present perfect exactly. Very often, the ordinary past tense covers that meaning.

Yes, this is about aspect, which is very important in Russian.

• ответить → perfective
• отвечать → imperfective

Here, ответил is from the perfective verb ответить, and it fits because replying is treated as a completed single action.

• ещё не ответил = he/she has not replied yet

If you said ещё не отвечал, that would sound different. It would suggest something more like:

• has not been replying
• has not given a reply at any point
• or it may sound less natural in this context

For a simple hasn’t replied yet, Russian normally prefers:

• ещё не ответил

No preposition is needed because the thing being replied to is simply not stated in this sentence.

The sentence only says:

• The recipient of the letter has not replied yet.

If you want to say reply to the letter, Russian often uses:

• ответить на письмо

So if you expanded the sentence, it might be:

• Получатель письма ещё не ответил на письмо.

That sounds repetitive, though, because the letter has already been mentioned. More natural possibilities might depend on context, for example:

• Получатель письма ещё не ответил нам. = The recipient of the letter has not replied to us yet.

Yes. Russian word order is fairly flexible, although the neutral order here is very natural:

• Получатель письма ещё не ответил.

Other orders are possible, but they change emphasis:

• Получатель письма не ответил ещё. — possible, but less neutral
• Ещё не ответил получатель письма. — emphasizes the fact that the reply still has not come
• Письма получатель ещё не ответил — not natural for this meaning

For learners, the original order is the safest and most neutral.

Yes, but there is a nuance.

• адресат письма = addressee, the person the letter is addressed to
• получатель письма = recipient, the person who receives the letter

In many contexts they can overlap, but they are not always identical:

• адресат focuses on who the letter is intended for
• получатель focuses on who receives it

In this sentence, получатель письма is perfectly natural.

No, the subject is explicitly stated here:

• Получатель письма

Russian can omit subjects in some contexts when they are obvious, but this sentence does not do that.

A shorter version might appear in conversation if the subject is already clear:

• Ещё не ответил. = He hasn’t replied yet.

But in your full sentence, the speaker clearly names the subject.

The noun and verb would need to match naturally.

If you used a feminine noun such as получательница:

• Получательница письма ещё не ответила.

If the subject were plural:

• Получатели письма ещё не ответили.

Notice the past tense endings:

• ответил = masculine singular
• ответила = feminine singular
• ответили = plural

The stress is:

• получа́тель
• письма́
• ещё
• отве́тил

So the sentence is pronounced:

• Получа́тель письма́ ещё не отве́тил.

Stress is important in Russian because it is not always predictable and can affect pronunciation quite a lot.