Impersonal constructions (можно, нужно, нельзя + dative)

Здесь можно сидеть. Мне нужно идти. Тебе нельзя курить. Нам надо поговорить.One can sit here. I need to go. You must not smoke. We need to talk.

Some Russian sentences have no grammatical subject at all. They say that something is allowed, needed or forbidden, or how someone feels, without naming a person who does it. This is called an impersonal construction. The person involved, if there is one, goes into the dative case (мне, тебе, ему, нам), and the word that carries the meaning is a short word that does not change: можно, нельзя, нужно, надо.

In short: a word such as можно (allowed, possible), нельзя (not allowed, not possible), нужно / надо (needed) is followed by an infinitive, and the person it applies to, if named, is in the dative: Мне нужно работать. The words never change for gender or number.

The main words

Нужно and надо are very close in meaning, and надо is a little more colloquial. In everyday speech, both are used all the time.

The person goes into the dative

To say who is allowed, needs or must not do something, put the person in the dative. The endings are in The dative case: addressee and age ("мне 20 лет"):

• Мне нужно идти. (I need to go.)
• Тебе надо отдохнуть. (You need to rest.)
• Ему нельзя пить кофе. (He is not allowed to drink coffee.)
• Детям можно играть здесь. (The children may play here.)
• Нам нужно поговорить. (We need to talk.)

Without a person, the sentence speaks about anyone in general: Здесь можно курить. (Smoking is allowed here.) В музее нельзя шуметь. (You must not make noise in the museum.) The answer to Можно? ("May I?") is often just можно or нельзя.

To ask permission, the question Можно + infinitive? is very common: Можно войти? (May I come in?) Можно вас спросить? (May I ask you something?) The verbs мочь, хотеть and уметь with a subject in the nominative are in Modal verbs + infinitive; the impersonal words in this article are the ones without a subject.

Past and future

The present tense has no verb. For the past, the neuter было is added, because the construction has no subject that could decide gender or number. For the future, будет is added:

• Мне нужно было уйти. (I had to leave.)
• Здесь нельзя было курить. (It was not allowed to smoke here.)
• Завтра можно будет отдохнуть. (Tomorrow we will be able to rest.)
• Вам надо будет позвонить. (You will need to call.)

Even when the dative person is a woman or plural, было stays the same: Ей нужно было уйти. Нам нужно было уйти.

Negatives: нельзя, не нужно, не надо

The word for "not allowed" is нельзя, not не можно. The words не нужно and не надо are the usual way to say that something is not needed, and often also that it is better not to do it:

• Вам не нужно приходить. (You do not need to come.)
• Не надо плакать. (Please don't cry. / There is no need to cry.)
• Тебе нельзя это есть. (You are not allowed to eat this.)

The difference to learn is that нельзя is a firm rule or a physical impossibility, while не нужно / не надо is "no need", often friendlier. A prohibition is нельзя курить, but a suggestion to skip something is не надо курить ("better not smoke"). The negation in general is in Negation with не.

With an infinitive after нельзя and не надо, the choice between the imperfective and the perfective often follows the aspect rules in Aspect in the past tense: the imperfective usually names a prohibited activity in general (Здесь нельзя курить), while the perfective points to one particular action. That action can be impossible (Эту дверь нельзя открыть, "This door cannot be opened") or ruled out on a given occasion (Сюда нельзя войти, "You must not go in here"). More about the aspects is in Verb aspect: imperfective and perfective.

Нужно or нужен?

Both come from the same adjective, and the choice depends on what is needed. With an infinitive, the neuter нужно is used: Мне нужно работать. With a noun, the short form agrees with the thing needed (Мне нужен словарь. Мне нужна книга. Нам нужны деньги.), as described in Short-form adjectives (рад, должен, готов). A neuter noun takes нужно too: Мне нужно время. (I need time.)

States and feelings with the dative

The same pattern, with a dative person and a word that does not change, describes how someone feels or what a situation is like. These words usually end in -о and look like adverbs:

• Мне холодно. (I am cold.)
• Ему жарко. (He is hot.)
• Нам весело. (We are having fun.)
• Ей скучно. (She is bored.)
• Мне стыдно. (I am ashamed.)

A few impersonal verbs follow the same dative pattern: Мне хочется спать. (I feel like sleeping.) Ему повезло. (He was lucky.) They change with the tense (Мне хотелось спать), unlike the words above.

Without a person, the same words describe the place or the weather: В комнате холодно. На улице жарко. Здесь очень тихо. In the past and the future, было and будет are added again: Вчера было холодно. Завтра будет жарко. Мне было скучно.

Common mistakes

• ❌ Я нужно идти → ✅ Мне нужно идти (The person is in the dative: мне)
• ❌ Она нужна было уйти → ✅ Ей нужно было уйти (The word does not change for the person; the past is нужно было, and the person is in the dative)
• ❌ Здесь не можно курить → ✅ Здесь нельзя курить (The negative of можно is нельзя)
• ❌ Мне нужна идти → ✅ Мне нужно идти (Before an infinitive, the neuter нужно is used)
• ❌ Я холодно → ✅ Мне холодно (A feeling is said with the dative, not the nominative)
• ❌ Мне нужен время → ✅ Мне нужно время (время is neuter, so the short form is нужно)

Quick check

Which word or form fits each gap?

1. ____ нужно идти домой. (I)
2. Здесь ____ курить. (not allowed)
3. Вчера ____ холодно. (the past)
4. ____ надо отдохнуть. (you, ты)
5. Мне ____ словарь. (needed, masculine noun)
6. Здесь ____ фотографировать. (allowed)

Key takeaways

• Impersonal sentences have no subject: можно, нельзя, нужно, надо + infinitive.
• The person involved goes into the dative: мне, тебе, ему, нам нужно идти.
• The words do not change; the past adds the neuter было and the future adds будет.
• Нельзя is the negative of можно; не нужно / не надо says "no need".
• With a noun, the short form agrees with it: нужен / нужна / нужно / нужны.
• States and feelings use the same pattern: мне холодно, ему скучно, нам весело.