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Frequent learner mistakes involving modal verbs.
Core modal verbs are followed by the base form of the main verb without to.
Common mistakes include can to swim instead of can swim and should to leave instead of should leave.
She can swim very well.
Она умеет очень хорошо плавать.
Can + base form without to.
You should leave now.
Тебе следует уйти сейчас.
Should + base form without to.
They might arrive soon.
Они могут скоро приехать.
Might + base form without to.
Core modal verbs do not take -s in the third person singular.
Use He can drive and She must leave, not He cans drive or She musts leave.
He can drive.
Он умеет водить машину.
No -s after can.
She must leave early.
Она должна уйти рано.
No -s after must.
It might rain later.
Позже может пойти дождь.
Might does not change for third person.
Core modal verbs normally form questions and negatives without do, does, or did.
Use Can you help? and She cannot come, not Do you can help? or She does not can come.
Can you help me?
Ты можешь мне помочь?
No do-support with can.
She cannot come.
Она не может прийти.
Negative without do.
Should we wait here?
Нам следует подождать здесь?
Question without do.
Use can for ordinary present ability and be able to when another tense or grammatical structure requires it.
For example, I can swim, but I will be able to swim after the course.
I can swim.
Я умею плавать.
Can for present ability.
I will be able to swim after the course.
Я смогу плавать после курса.
Be able to for future ability because can has no future form.
She has been able to work remotely.
Она смогла работать удалённо.
Be able to in present perfect.
Could commonly describes general past ability, while was or were able to is often used for a specific successful achievement.
Compare I could swim when I was five with I was able to fix the problem yesterday.
I could swim when I was five.
Я умел плавать в пять лет.
Could for general past ability.
I was able to fix the problem yesterday.
Вчера мне удалось исправить проблему.
Was able to for specific achievement.
She could read when she was four.
Она умела читать в четыре года.
Could for general past ability.
Can does not normally have a future form for ability, so will be able to is generally used.
Use I will be able to help tomorrow rather than I can help tomorrow when the meaning is future ability.
I will be able to help tomorrow.
Я смогу помочь завтра.
Use will be able to, not can, for future ability.
She can speak Spanish now.
Она умеет говорить по-испански сейчас.
Can for present ability.
They will be able to attend the meeting.
Они смогут присутствовать на встрече.
Future ability with will be able to.
Must and have to can both express obligation, but their use depends on meaning, source of obligation, tense, and context.
Must often presents an obligation directly, while have to commonly describes external necessity. Had to is normally used for past necessity.
I must call my mother.
Я должен позвонить маме.
Must: personal obligation.
I have to wear a uniform at work.
На работе мне нужно носить форму.
Have to: external rule.
I had to leave early yesterday.
Вчера мне пришлось уйти рано.
Had to for past necessity; must has no past form.
Must not expresses prohibition, while do not have to expresses lack of necessity.
Compare You must not enter with You do not have to enter.
You must not enter this area.
Вам нельзя входить в эту зону.
Must not: prohibition.
You do not have to enter if you don't want to.
Вам не обязательно входить, если не хотите.
Do not have to: lack of necessity.
We must not be late.
Нам нельзя опаздывать.
Prohibition.
Should generally expresses advice or recommendation, while must expresses stronger obligation or necessity.
Compare You should see a doctor with You must see a doctor.
You should see a doctor.
Тебе следует обратиться к врачу.
Should: advice.
You must see a doctor.
Ты должен обратиться к врачу.
Must: strong obligation.
We should leave soon.
Нам следует скоро уйти.
Weaker recommendation.
Should and ought to have similar meanings in many contexts, but should is more common in everyday English.
Ought to can sound more formal or less conversational.
You should apologize.
Тебе следует извиниться.
Should is common in everyday English.
You ought to apologize.
Тебе следует извиниться.
Ought to is more formal, less common in speech.
We should be more careful.
Нам следует быть осторожнее.
Should preferred.
Can and may can both ask for permission, but may is generally more formal.
For example, Can I leave early? is common in conversation, while May I leave early? is more formal.
Can I leave early?
Можно мне уйти рано?
Can: informal permission.
May I leave early?
Можно мне уйти рано?
May: formal permission.
You can use my phone.
Ты можешь воспользоваться моим телефоном.
Giving permission informally.
Could can express past ability or a polite request for permission depending on context.
Compare I could swim when I was young with Could I borrow your phone?
I could swim when I was young.
Я умел плавать в детстве.
Could: past ability.
Could I borrow your phone?
Можно одолжить твой телефон?
Could: polite permission request.
Could you help me?
Не могли бы вы мне помочь?
Polite request with could.
Can can express either ability or permission.
Compare Can you drive? with Can I drive your car?
Can you drive?
Ты умеешь водить машину?
Can for ability.
Can I drive your car?
Можно мне повести твою машину?
Can for permission.
He can speak French.
Он умеет говорить по-французски.
Ability.
May and might can both express possibility, and the difference is often one of tentativeness or context rather than a fixed probability scale.
Both It may rain and It might rain can describe a possible future event.
It may rain tomorrow.
Завтра, возможно, пойдёт дождь.
May: possibility, somewhat more likely.
It might rain tomorrow.
Завтра, возможно, пойдёт дождь.
Might: more tentative possibility.
She may be at home.
Она, возможно, дома.
May for present possibility.
Must can express either strong obligation or a strong logical conclusion.
Compare You must leave now with She must be at home. Context determines whether must expresses obligation or deduction.
You must leave now.
Ты должен уйти сейчас.
Must for obligation.
She must be at home.
Она, должно быть, дома.
Must for deduction.
He must be tired after work.
Он, должно быть, устал после работы.
Deduction.
Must have + past participle expresses deduction about the past, while had to expresses past obligation or necessity.
Compare She must have forgotten with She had to leave early.
She must have forgotten.
Она, должно быть, забыла.
Must have: deduction about past.
She had to leave early.
Ей пришлось уйти рано.
Had to: past obligation.
They must have missed the bus.
Они, должно быть, опоздали на автобус.
Past deduction.
Should have + past participle normally expresses past advice, criticism, or an unfulfilled expectation, while must have expresses a strong deduction about the past.
Compare You should have called me with You must have forgotten to call me.
You should have called me.
Тебе следовало позвонить мне.
Should have: criticism/regret about past.
You must have forgotten to call me.
Ты, должно быть, забыл позвонить мне.
Must have: deduction about past.
She should have arrived earlier.
Ей следовало приехать раньше.
Past expectation/criticism.
Could have + past participle can express past possibility, an unrealized opportunity, or a possible alternative explanation.
For example, He could have missed the train and We could have won the game.
He could have missed the train.
Он, возможно, опоздал на поезд.
Could have: past possibility.
We could have won the game.
Мы могли бы выиграть игру.
Unrealized opportunity.
She could have been delayed by traffic.
Её могли задержать пробки.
Possible explanation for past.
Need not have usually suggests that an unnecessary action was nevertheless performed, while did not need to focuses on lack of necessity.
Compare You need not have bought food, but you did with You did not need to buy food, so you did not.
You need not have bought food, but you did.
Тебе не нужно было покупать еду, но ты купил.
Need not have: action done though unnecessary.
You did not need to buy food, so you did not.
Тебе не нужно было покупать еду, поэтому ты и не купил.
Did not need to: no action taken.
She need not have worried; the exam was easy.
Ей не стоило волноваться; экзамен был лёгким.
Unnecessary worry in past.
Had better is followed by the base form and expresses strong advice, often with an implied consequence.
Use You had better leave now, not You had better to leave now.
You had better leave now.
Тебе лучше уйти сейчас.
Strong advice with implied consequence.
We had better take an umbrella.
Нам лучше взять зонт.
Advice based on situation.
She had better not be late again.
Ей лучше снова не опаздывать.
Negative strong advice.
Be supposed to is followed by to and commonly expresses expectation, arrangement, or duty.
For example, You are supposed to be here at nine and We are supposed to submit the form today.
You are supposed to be here at nine.
Ты должен быть здесь в девять.
Expectation/duty.
We are supposed to submit the form today.
Мы должны подать форму сегодня.
Arrangement/duty.
The train is supposed to arrive at six.
Поезд должен прибыть в шесть.
Scheduled expectation.
Used to describes past habits or states, while be used to means being accustomed to something.
Compare I used to wake up early with I am used to waking up early.
I used to wake up early.
Раньше я просыпался рано.
Used to: past habit.
I am used to waking up early.
Я привык рано вставать.
Be used to + gerund: accustomed to.
She used to live in London.
Она раньше жила в Лондоне.
Past state with used to.
Use modal + have + past participle for many meanings referring to the past.
Common mistakes include modal + had or modal + past tense instead of modal + have + past participle.
She may have left.
Она, возможно, ушла.
Modal + have + past participle.
They must have forgotten.
Они, должно быть, забыли.
Past deduction.
He should have called earlier.
Ему следовало позвонить раньше.
Past advice/criticism.
Use modal + be + verb-ing to describe an ongoing activity.
For example, She may be working. A common mistake is omitting be and saying She may working.
She may be working now.
Она, возможно, сейчас работает.
Modal + be + verb-ing.
They must be waiting outside.
Они, должно быть, ждут снаружи.
Deduction about ongoing activity.
He could be sleeping.
Он, возможно, спит.
Possibility about ongoing.
Use modal + be + past participle for passive constructions.
For example, The form must be completed and The documents should be signed.
The form must be completed.
Форма должна быть заполнена.
Modal + be + past participle.
The documents should be signed.
Документы должны быть подписаны.
Passive with should.
The door can be opened from outside.
Дверь можно открыть снаружи.
Can passive.
Core modal verbs are generally not combined directly with another core modal verb.
Use alternatives such as will be able to, may have to, or might be able to instead of combining two core modals directly.
She will be able to come.
Она сможет прийти.
Use be able to instead of will can.
We may have to leave early.
Нам, возможно, придётся уйти рано.
May + have to instead of may must.
He might be able to help.
Он, возможно, сможет помочь.
Might + be able to.
Choose modal expressions appropriate to the level of formality and the social context.
For example, may is often more formal than can for permission, while ought to is less common in casual conversation than should.
May I come in?
Можно войти?
Formal permission.
Can I come in?
Можно войти?
Informal permission.
You ought to apologize.
Вам следует извиниться.
Ought to is more formal than should.
Use a modal only when its meaning contributes to the intended statement.
Avoid adding modals where a simple declarative form is sufficient, especially when expressing facts or certainty.
I can swim.
Я умею плавать.
Modal is appropriate for ability.
She works in London.
Она работает в Лондоне.
No modal needed for simple fact.
Water boils at 100°C.
Вода кипит при 100°C.
Fact without modal.
Modal choice depends on meaning, time reference, certainty, obligation, permission, ability, politeness, and context.
The most common errors occur when learners translate modal meanings directly from another language or assume that one English modal has only one meaning.
You must wear a seat belt.
Ты должен пристегнуть ремень.
Must for obligation.
She may be at home.
Она, возможно, дома.
May for possibility.
Could you open the window?
Не могли бы вы открыть окно?
Could for polite request.
Accurate modal usage requires control of both grammatical patterns and semantic distinctions.
Review the differences between ability, permission, obligation, advice, possibility, deduction, prediction, willingness, habitual behaviour, and past modal meanings.
He cans swim.
Он умеет плавать.
Incorrect: no -s after modal.
She must to leave.
Она должна уйти.
Incorrect: no to after must.
Do you can help?
Ты можешь помочь?
Incorrect: no do-support with modals.