Позвоните немедленно.

Позвоните is a verb in the imperative form, so it means call! or please call!

More specifically, it comes from the infinitive позвонить (to call / to phone) and is the plural or polite imperative form.

So this form can be used:

• when speaking to more than one person
• when speaking to one person formally or politely

The ending -ите is typical of many plural/formal imperative forms in Russian.

Compare:

• позвони = call! (to one person informally)
• позвоните = call! (to several people, or to one person politely)

This is similar to the difference between informal and polite/plural you in many European languages, even though modern English uses just you for both.

Yes, Позвоните немедленно sounds either:

• polite/formal if said to one person, or
• plural if said to several people

Because of -ите, a learner will usually understand it as more formal than Позвони немедленно.

That said, the word немедленно (immediately) makes the whole sentence sound quite strong and urgent, so even though the verb form is polite/formal, the overall tone is still very direct.

This is about aspect, which is very important in Russian verbs.

• позвонить is perfective
• звонить is imperfective

In an imperative, perfective often means do this once and complete it. So:

• Позвоните = make the call / call once / call and complete the action
• Звоните can mean something more like call, be calling, call regularly, or in some contexts feel free to call

So in a sentence like Позвоните немедленно, the perfective form is natural because the speaker wants one specific completed action: make the phone call now.

Немедленно is an adverb. It describes how the action should be done.

It means:

• immediately
• without delay
• at once

Because it is an adverb, it does not change for gender, number, or case.

The stress is:

• позвони́те
• неме́дленно

So you can pronounce the sentence roughly as:

paz-va-NEE-tye nye-MED-len-na

A more natural English-style approximation is only approximate, of course, but the important thing for learners is the stressed syllables:

• -ни́- in позвони́те
• -ме́- in неме́дленно

Yes. Russian word order is more flexible than English.

You can say:

• Позвоните немедленно.
• Немедленно позвоните.

Both mean basically the same thing, but the emphasis changes a little.

• Позвоните немедленно is neutral and natural.
• Немедленно позвоните puts stronger focus on immediately.

So moving немедленно to the front can make the urgency feel even stronger.

In Russian, the subject is often omitted when it is clear from the verb form.

Here, позвоните already tells you that the command is directed to:

• you (plural), or
• you (formal singular)

So adding вы is usually unnecessary.

You could say Вы позвоните немедленно, but that would usually sound marked, emphatic, or context-dependent rather than neutral.

It can be either, depending on tone and context.

Russian imperatives do not automatically include a separate word for please. So Позвоните by itself can sound:

• like a straightforward instruction: Call immediately
• or, with polite intonation/context, like Please call immediately

If you want to make it explicitly more polite, you could add пожалуйста:

• Позвоните немедленно, пожалуйста.

But because немедленно is so urgent, even with пожалуйста the sentence still sounds strong.

Немедленно is usually stronger and more formal-sounding than сразу.

• немедленно = immediately, without any delay
• сразу = right away / at once

Both can work in urgent situations, but немедленно often sounds more forceful, official, or dramatic.

Compare:

• Позвоните сразу. = Call right away.
• Позвоните немедленно. = Call immediately.

The second one usually feels more urgent.

The infinitive is позвонить.

A useful way to think about it is:

• звонить = to call / to ring
• по-
  • звонить = позвонить

The prefix по- often helps create a perfective verb, giving the idea of a single completed action. In this sentence, that fits well: the speaker wants one completed phone call.

So:

• позвонить = to make a call
• позвоните = call! / please call!

In modern everyday usage, позвонить usually means to call someone by phone.

Historically and literally, it is related to ringing or sounding, but in normal modern contexts, learners should understand Позвоните as give a phone call.

So in this sentence, Позвоните немедленно is naturally understood as:

• Call immediately
• specifically, phone immediately