English has a tidy row of modal verbs — helpers such as can, must, may and need that sit in front of another verb. Russian divides those jobs among impersonal words (мо́жно, нельзя́, на́до, ну́жно), the short adjective до́лжен, and the ordinary conjugated verb мочь ("to be able"). The important first choice is meaning: permission is not the same thing as ability.
The patterns that make it click
With мо́жно, нельзя́, на́до and ну́жно, there is no ordinary subject: the sentence is impersonal, and a named person sits in the dative case (мне, тебе́, ему́, ей, нам, вам, им). The verb мочь instead takes a normal nominative subject and conjugates (я могу́, ты мо́жешь). До́лжен also has a nominative subject, but changes like a short adjective to match gender and number.
| Word | Rough meaning | The person is… | Example |
|---|
| мо́жно | may, can (allowed / possible) | dative (often none at all) | Мо́жно войти́? — May I come in? |
| мочь (могу́) | can, be able | nominative | Я могу́ подня́ть коро́бку. — I can lift the box. |
| нельзя́ | mustn't, can't | dative (often none at all) | Здесь нельзя́ кури́ть. — You mustn't smoke here. |
| на́до / ну́жно | need to, have to | dative | Мне на́до идти́. — I have to go. |
| до́лжен | must, be obliged to | nominative (and it agrees) | Я до́лжен идти́. — I must go. |
Notice that мо́жно and нельзя́ very often appear with no person named at all — Мо́жно войти́? is simply "May I / May one come in?", and context tells you who. When you do name the person, add them in the dative: Вам мо́жно ("You're allowed to"). For personal ability, switch patterns: Вы мо́жете means "You can / are able to."
Можно, мочь and нельзя: permission, ability and prohibition
Мо́жно plus an infinitive asks for or grants permission, or states that something is possible. It's the polite little word you'll use dozens of times a day:
- Мо́жно войти́? — May I come in?
- Мо́жно посмотре́ть? — May I take a look?
- Здесь мо́жно фотографи́ровать. — You're allowed to take photos here.
On its own, Мо́жно? is a complete, useful question — "Is it OK? / May I?" — when you reach for something or step toward a seat.
Use мочь when "can" means that someone has the ability or situational capacity to do something: Я могу́ подня́ть коро́бку ("I can lift the box") and Она́ мо́жет прийти́ за́втра ("She can come tomorrow"). It is a verb, so it conjugates. Compare Мне мо́жно войти́? ("Am I allowed to come in?") with Я могу́ войти́ ("I am able to come in").
Нельзя́ is the negative impersonal word, and a common beginner pattern links its meaning to aspect — whether the following verb presents an activity (imperfective) or a bounded result (perfective). If that pairing is new, start with Russian verb aspect. In the standard teaching contrast:
- Нельзя́ + imperfective = a prohibition. It isn't allowed. Здесь нельзя́ кури́ть ("You mustn't smoke here"); Нельзя́ открыва́ть окно́ ("The window mustn't be opened").
- Нельзя́ + perfective = an impossibility. It simply can't be done. Нельзя́ откры́ть дверь — она́ закры́та на ключ ("The door can't be opened — it's locked").
Use this as a strong tendency, not a mechanical law: prohibition commonly takes the imperfective (кури́ть, открыва́ть), while impossibility commonly takes the perfective (откры́ть). Context and the kind of action still matter.
Надо and нужно: when you simply need to
For plain necessity — "I need to," "we have to" — Russian offers two near-twins, на́до and ну́жно. Before an infinitive they are usually interchangeable; the person stays in the dative and the word itself never changes:
- Мне на́до идти́. — I have to go.
- Нам ну́жно отдохну́ть. — We need to rest.
- Тебе́ ну́жно бо́льше спать. — You need to sleep more.
The difference is tone, not grammar: на́до is very common in speech and can feel direct and conversational, while ну́жно sounds a shade more neutral. Pick either and you'll be understood.
One twist worth having ready: when you need a thing rather than an action — a ticket, a map, documents — ну́жно turns into an adjective and agrees with the thing you need. (A short adjective here just means the predicate form you use after "is," like glad in "I am glad.") The forms are ну́жен / нужна́ / ну́жно / нужны́, and the person still sits in the dative:
| Form | Agrees with | Example |
|---|
| ну́жен | a masculine noun | Мне ну́жен биле́т. — I need a ticket. |
| нужна́ | a feminine noun | Мне нужна́ ка́рта. — I need a map. |
| ну́жно | a neuter noun | Мне ну́жно вре́мя. — I need time. |
| нужны́ | a plural noun | Мне нужны́ докуме́нты. — I need documents. |
So Мне ну́жно купи́ть биле́т ("I need to buy a ticket," with an infinitive) uses the frozen ну́жно, but Мне ну́жен биле́т ("I need a ticket," with a noun) uses the agreeing ну́жен. The thing you need has quietly become the grammatical subject.
Должен: the modal that agrees
До́лжен is the odd one out, and the giveaway is that it has a real nominative subject. It's a short adjective, so it agrees in gender and number with whoever is obliged:
| Subject | Form | Example |
|---|
| он / я (male) | до́лжен | Он до́лжен рабо́тать. — He has to work. |
| она́ / я (female) | должна́ | Она́ должна́ рабо́тать. — She has to work. |
| оно́ | должно́ | Э́то должно́ быть здесь. — It should be here. |
| они́ / мы / вы | должны́ | Они́ должны́ рабо́тать. — They have to work. |
Meaning-wise, до́лжен carries more weight than на́до or ну́жно. It leans toward duty, rule, expectation or being supposed to: Вы должны́ извини́ться ("You must apologise"), Я до́лжен быть в о́фисе в де́вять ("I'm supposed to be at the office at nine"). Use на́до/ну́жно for a practical need and до́лжен for an obligation.
One handy side meaning: до́лжен also means "to owe." Я до́лжен тебе́ сто рубле́й is "I owe you a hundred roubles" — the same adjective, still agreeing with the person who owes.
Past and future: just add было, будет (or был, буду)
These words have no past or future tense of their own, so Russian supplies one. The impersonal group — мо́жно, нельзя́, на́до, ну́жно — simply adds the frozen neuter бы́ло for the past and бу́дет for the future. До́лжен, being an adjective, takes был / бу́ду and keeps agreeing:
| Now | Past | Future |
|---|
Мне на́до идти́.
I have to go. | Мне на́до бы́ло идти́.
I had to go. | Мне на́до бу́дет идти́.
I'll have to go. |
Я до́лжен идти́.
I must go. | Я до́лжен был идти́.
I had to go. | Я до́лжен бу́ду идти́.
I'll have to go. |
A woman would say Я должна́ была́ идти́ and Я должна́ бу́ду идти́ — the adjective and its был both shift to the feminine. The impersonal бы́ло never changes, which is one reason beginners often reach for на́до and ну́жно first.
Questions people actually ask
What is the difference between можно and мочь? Можно is impersonal and normally asks or states permission or general possibility: Мне можно войти? means "May I come in?" Мочь is a conjugated verb for someone's ability or situational capacity: Я могу поднять коробку means "I can lift the box."
How do you say "I have to" in Russian? Use надо or нужно with the person in the dative and an infinitive: Мне надо идти or Мне нужно идти means "I have to go". For a stronger sense of duty, use должен, which agrees with the subject: Я должен идти for a man, Я должна идти for a woman.
What is the difference between надо, нужно and должен? Надо and нужно are impersonal: the person goes in the dative and the word itself never changes, as in Нам нужно отдохнуть. Должен is a short adjective that agrees in gender and number with a nominative subject — он должен, она должна, они должны — and leans toward obligation or expectation rather than a simple practical need.
Does нельзя mean "mustn't" or "can't"? Both. A useful beginner pattern is that нельзя with an imperfective verb often marks prohibition, while нельзя with a perfective verb often marks impossibility. Context still controls the meaning, so treat that as a strong tendency rather than an exceptionless decoder.
How do you put можно, надо or нужно in the past? Add было: Мне надо было уйти means "I had to leave". For the future, add будет: Тебе нельзя будет опаздывать means "You won't be allowed to be late". Должен instead uses был and буду and agrees with the subject: Я должен был уйти.
Try it with your own day: say three things you have to do with мне на́до, one thing you're allowed to do with мне мо́жно, and one thing you mustn't with нельзя́. If you'd rather drill these out loud with instant correction than second-guess the dative, that's exactly what we build — start your seven-day free trial — no card required. New to the app? Search “Gora Academy” in the Apple App Store or Google Play, or open it on the web.