Learn Hardcore Russian: Пожалуйста, не звони поздно ночью.

Звони is the 2nd-person singular imperative of the imperfective verb звонить. It addresses one person informally (the ты form). So the sentence is a polite request to someone you talk to as ты.

How do I say it to more than one person or politely?

Use the вы-form of the imperative: Пожалуйста, не звоните поздно ночью. That can address multiple people or one person formally.

Why is it звони (imperfective) and not позвони (perfective) after не?

In negative imperatives, Russian usually uses the imperfective: Не звони = “Don’t (ever/in general) call.” The perfective negative imperative (Не позвони) is rare and sounds unnatural or very marked here. There are exceptions with certain verbs (e.g., Не забудь “Don’t forget”).

If I want to be explicit that they shouldn’t call me, where do I put мне?

Say: Пожалуйста, не звони мне поздно ночью. The verb звонить governs the dative case: звонить кому? — мне, маме, врачу. With institutions, you’ll often hear звонить в банк/в полицию as well.

How polite is this sentence? Is it a request or a command?

With пожалуйста, it’s a courteous request. Without пожалуйста (Не звони поздно ночью) it becomes a blunt order. You can soften further with phrases like Пожалуйста, очень прошу, не звони поздно ночью.

Can I put пожалуйста at the end instead of the beginning?

Yes: Не звони поздно ночью, пожалуйста. It’s equally natural. Beginning placement can sound a touch more formal; end placement can feel a bit more conversational.

Why is there a comma after Пожалуйста?

When пожалуйста is used as an introductory parenthetical (“please”), it’s set off by a comma: Пожалуйста, …. If пожалуйста modifies a specific word within the sentence, commas may be omitted, but in requests like this the comma is standard.

What does ночью mean grammatically, and why isn’t there a в?

Ночью is the instrumental singular of ночь used adverbially, meaning “at night.” Russian commonly uses instrumental adverbs for times of day: утром, днём, вечером, ночью. No preposition is needed.

Is поздно ночью the only/most natural way to say “late at night”?

It’s very natural. Alternatives:

поздней ночью (slightly more literary)
глубокой ночью (“in the dead of night”)
среди ночи (“in the middle of the night”)
Habitual: по ночам (“at nights”): Не звони по ночам.

Can I move the time phrase earlier, like Пожалуйста, поздно ночью не звони?

Yes. Word order is flexible. Putting поздно ночью earlier foregrounds the time. The most neutral placement is after the verb, as in the original.

Where is the word for “phone”? Do I need по телефону?

Звонить already means “to call (by phone).” Adding по телефону is possible but usually redundant. Avoid звонить на телефон when you mean “call someone”; say звонить кому or звонить в (организацию).

How do I say “Don’t call so/too late at night”?

“so late”: Пожалуйста, не звони так поздно ночью.
“too late”: Пожалуйста, не звони слишком поздно ночью.

What’s the difference between звони and позвони in affirmative commands?

Позвони (perfective): make one call (“Give me a call (once)”).
Звони (imperfective): call repeatedly/regularly or keep calling (“Call me (whenever/regularly)”). In the negative, stick with Не звони for the natural prohibition.

Why is it не, not ни in не звони?

Не is the standard negation with verbs, including imperatives. Ни is an intensifier used with negative pronouns/adverbs (e.g., никогда, никуда) or for emphasis in double negation, but not to negate the verb by itself.

Is поздно ночью ever redundant? Isn’t “night” already late?

No. Ночью just means “at night.” Поздно ночью narrows it to a later part of the night (e.g., after midnight), adding useful nuance.

How do I put this on a sign or general notice?

Use the infinitive or a noun phrase:

Пожалуйста, не звонить поздно ночью.
Просьба не звонить после 22:00. These are impersonal and address anyone who reads them.

How do I pronounce it and where is the stress?

Stresses: пожалу́йста, не звони́ по́здно но́чью. Hints:

ж in пожалу́йста is like the “s” in “measure.”
ч in но́чью is soft [tɕ]; the ью sounds like “yoo” after a soft consonant.
звони́ has stress on the last syllable.