Permission and Prohibition: Можно, Нельзя | Russian Grammar

Russian asks and grants permission with a single impersonal word, мо́жно ("it's allowed / it's possible"), and forbids with its negative, нельзя́. Neither is a conjugated verb — there's no subject, the word never changes form, and the person, if mentioned, sits in the dative. The genuinely tricky part is hidden in нельзя́: depending on the aspect of the verb that follows it, нельзя́ means either "you mustn't" or "it's impossible". This page covers both words and then unpacks that aspect split, which is one of the highest-value details in everyday Russian.

мо́жно — may / it's allowed / it's possible

мо́жно grants or asks for permission, or states that something is possible. There is no subject; the person, when named, goes in the dative. Without a dative it's a general "is it allowed?".

Здесь мо́жно кури́ть?

Is smoking allowed here? (general permission — no personal subject)

Мне мо́жно войти́?

May I come in? (dative мне; permission for myself)

Извини́те, мо́жно вопро́с?

Excuse me, may I ask a question? (a fixed polite formula: мо́жно + noun, infinitive understood)

In shops, cafés, and any service situation, мо́жно + a noun is the everyday way to ask for something — the infinitive (дать, взять, посмотре́ть) is simply left out because everyone supplies it:

Мо́жно меню́, пожа́луйста?

Could I have the menu, please? (мо́жно + noun меню́ — '[may I have] the menu')

Мо́жно мне ещё ча́ю?

Could I have some more tea? (dative мне + partitive genitive ча́ю — a polite café request)

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мо́жно + a noun is your single most useful politeness tool as a beginner. Мо́жно во́ду? / Мо́жно счёт? / Мо́жно э́то? — "Could I have water / the bill / this?" It sidesteps a whole verb and is perfectly natural. More request patterns are on permission requests.

нельзя́ — the negative of мо́жно

The opposite of мо́жно is нельзя́ — there is no не мо́жно in Russian (that form does not exist). нельзя́ is also impersonal, also takes an optional dative person, and also never changes form.

Тебе́ нельзя́ так мно́го рабо́тать.

You shouldn't work so much. (dative тебе́; a caring prohibition)

Здесь нельзя́ паркова́ться.

You can't park here. (a general rule — no smoking, no parking — no dative)

So far нельзя́ looks like a simple "not allowed". But the word is doing double duty, and the aspect of the following infinitive decides which job it's doing.

The aspect split — the key point of this page

нельзя́ has two distinct meanings, and you tell them apart by the aspect of the infinitive after it:

нельзя́ + IMPERFECTIVE = prohibition — "you mustn't / it's forbidden". The action is possible; it's just not allowed.
нельзя́ + PERFECTIVE = impossibility — "you can't manage to / it can't be done". Nobody's forbidding it; it simply isn't achievable.

The same word, two readings, sorted purely by aspect. (If you need to review what imperfective vs perfective means, see verbal aspect overview.)

Sentence	Aspect of infinitive	Meaning
Здесь нельзя́ кури́ть.	imperfective (кури́ть)	No smoking here. (forbidden)
Э́ту дверь нельзя́ откры́ть.	perfective (откры́ть)	This door can't be opened. (impossible)

нельзя́ + imperfective = prohibition

The imperfective names the activity as a whole, and нельзя́ bans it. This is the "no smoking / no entry / you mustn't" reading.

В библиоте́ке нельзя́ разгова́ривать гро́мко.

You mustn't talk loudly in the library. (imperfective разгова́ривать → a rule against the activity)

Тебе́ нельзя́ есть сла́дкое — ты же на дие́те.

You're not allowed sweets — you're on a diet. (imperfective есть → prohibition)

Здесь нельзя́ фотографи́ровать.

Photography isn't allowed here. (imperfective → a posted rule)

нельзя́ + perfective = impossibility

The perfective names a completed result, and нельзя́ says that result can't be reached. This is "it's impossible / there's no way to / you can't manage to".

Э́ту дверь нельзя́ откры́ть — она́ за́перта.

This door can't be opened — it's locked. (perfective откры́ть → impossibility, not a rule)

Здесь ничего́ нельзя́ поде́лать.

There's nothing to be done here. (perfective поде́лать → it's hopeless, impossible)

Его́ по́черк нельзя́ разобра́ть.

His handwriting can't be made out. (perfective разобра́ть → impossible to decipher)

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Decide which нельзя́ you mean before you pick the infinitive. Are you banning an activity (no smoking)? Use the imperfective — нельзя́ кури́ть. Are you saying a result can't be achieved (can't get it open)? Use the perfective — нельзя́ откры́ть. Mixing them up produces real comprehension errors: Дверь нельзя́ открыва́ть (imperfective) means "you're not allowed to open the door", which is very different from Дверь нельзя́ откры́ть (perfective) "the door can't be opened".

This contrast is worth dwelling on, because almost no beginner course flags it, and it bites in both directions. A learner who says Э́ту зада́чу нельзя́ реша́ть (imperfective) when they mean "this problem can't be solved" has accidentally said "you're forbidden to work on this problem" — the perfective нельзя́ реши́ть is what carries "it's unsolvable".

Past and future

Being impersonal, мо́жно and нельзя́ take the frozen neuter бы́ло (past) and бу́дет (future), never agreeing with the dative person:

Ра́ньше здесь мо́жно бы́ло кури́ть.

You used to be allowed to smoke here. (past: мо́жно + frozen neuter бы́ло)

Тебе́ нельзя́ бу́дет опа́здывать на но́вой рабо́те.

You won't be allowed to be late at the new job. (future: нельзя́ + frozen neuter бу́дет)

The full impersonal-modal frame, including мо́жно and нельзя́ alongside на́до, ну́жно, and пора́, is drilled on dative with impersonal modals. For the verb мочь (the conjugated "can") and its skill-counterpart уме́ть, see Мочь vs Уметь; for до́лжен and на́до, see Должен, Надо, Нужно.

Common Mistakes

❌ Здесь не мо́жно кури́ть.

Incorrect — there is no *не мо́жно. The negative of мо́жно is нельзя́.

✅ Здесь нельзя́ кури́ть.

No smoking here. (нельзя́ = prohibition; imperfective кури́ть)

❌ Э́ту дверь нельзя́ открыва́ть — она́ за́перта.

Wrong aspect for the intended meaning — imperfective открыва́ть makes this 'you're forbidden to open the door'. For 'it can't be opened', use the perfective.

✅ Э́ту дверь нельзя́ откры́ть — она́ за́перта.

This door can't be opened — it's locked. (perfective откры́ть = impossibility)

❌ Здесь нельзя́ закури́ть.

Wrong aspect for a posted rule — perfective закури́ть reads as 'one can't manage to light up' (e.g. it's too windy), not 'smoking is banned'.

✅ Здесь нельзя́ кури́ть.

Smoking is forbidden here. (imperfective кури́ть = prohibition)

❌ Я мо́жно войти́?

Incorrect — мо́жно is impersonal and takes a dative, not a nominative. Use мне.

✅ Мне мо́жно войти́?

May I come in? (dative мне + impersonal мо́жно)

❌ Ей нельзя́ была́ е́здить.

Incorrect — нельзя́ is impersonal, so the past is frozen neuter бы́ло, not была́.

✅ Ей нельзя́ бы́ло е́здить.

She wasn't allowed to travel. (dative ей + frozen neuter бы́ло)

Key Takeaways

мо́жно = may / it's allowed / it's possible; impersonal, optional dative person: Здесь мо́жно? Мне мо́жно войти́? Мо́жно меню́?
The opposite of мо́жно is нельзя́ — there is no не мо́жно.
нельзя́ + imperfective = prohibition ("you mustn't"): Здесь нельзя́ кури́ть.
нельзя́ + perfective = impossibility ("it can't be done"): Э́ту дверь нельзя́ откры́ть.
Decide the meaning first, then choose the aspect — getting it backwards swaps "forbidden" and "impossible".
Both are impersonal: dative person, frozen neuter бы́ло / бу́дет in the past and future (Ра́ньше мо́жно бы́ло…, нельзя́ бу́дет…).

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