Мочь (to be able / can) | Russian Grammar

Infinitive: мочь — "to be able to, can" Aspect: imperfective Perfective: смочь ("to manage to, to succeed in being able")

мочь is the everyday "can" of Russian — the verb you reach for when something is possible or you have the power to do it. It is irregular in two famous ways: the present alternates between г and ж (могу́ but мо́жешь), and the past has no -л in the masculine (мог, not \мочил). It also lacks a usable imperative. The single most important thing to get right alongside the forms is the boundary with уме́ть — both translate as English "can," but they cover different ground. Stress is marked on every form.

Present tense — the г/ж alternation

Person	Form	Stem consonant
я	могу́	г
ты	мо́жешь	ж
он / она́ / оно́	мо́жет	ж
мы	мо́жем	ж
вы	мо́жете	ж
они́	мо́гут	г

The pattern is tidy once you see it: the stem has г in the two "outer" forms — я (могу́) and они́ (мо́гут) — and ж in the four "inner" forms (мо́жешь, мо́жет, мо́жем, мо́жете). This г/ж split is a survival of an old Slavic sound law and shows up in a small family of verbs. The stress also shifts: end-stressed in могу́, then stem-stressed everywhere else (мо́жешь, мо́жет…). So я is the odd one out on both counts — г and end-stress.

Я не могу́ найти́ свои́ ключи́.

I can't find my keys. — могу́, the я form: г + end-stress.

Ты мо́жешь говори́ть поме́дленнее?

Can you speak a bit more slowly? — мо́жешь, the ты form: ж + stem-stress. A polite request.

Они́ мо́гут прийти́ за́втра.

They can come tomorrow. — мо́гут, the они́ form: back to г.

Past tense — no masculine -л

This is the second irregularity. Russian past tenses normally end in -л in the masculine (был, чита́л), but a small set of verbs with stems ending in a consonant drop the -л in the masculine only. мочь is the headline example: the masculine is bare мог, while the feminine, neuter, and plural add their endings to a г-stem and are end-stressed.

Gender / number	Form	Note
masculine	мог	no -л; stem-stress
feminine	могла́	end-stress
neuter	могло́	end-stress
plural	могли́	end-stress

Я не мог усну́ть всю ночь.

I couldn't fall asleep all night. — masculine мог: no -л. (A woman would say не могла́.)

Она́ не могла́ поня́ть, в чём де́ло.

She couldn't understand what was going on. — feminine могла́, end-stressed.

Мы могли́ бы помо́чь, е́сли бы зна́ли ра́ньше.

We could have helped if we'd known earlier. — могли́ + бы = the conditional 'could have'.

That last example shows a high-frequency use: мог бы / могла́ бы / могли́ бы ("could / could have") is the polite conditional of мочь, used constantly for soft requests and hypotheticals.

Future tense

мочь is imperfective; in practice the future is carried by the perfective смочь ("to manage to be able"), which has a simple future. The compound бу́ду мочь exists but is rarely used — "can" in the future is normally expressed with смогу́.

Person	perfective смочь (future)
я	смогу́
ты	смо́жешь
он / она́ / оно́	смо́жет
мы	смо́жем
вы	смо́жете
они́	смо́гут

смочь mirrors мочь exactly — same г/ж alternation (смогу́ / смо́жешь / смо́гут), same past with no masculine -л (смог, смогла́, смогло́, смогли́). The prefix с- adds the sense of managing to / succeeding at a single occasion.

Извини́, я не смогу́ прийти́ за́втра.

Sorry, I won't be able to come tomorrow. — смогу́, perfective future. The default way to say 'I won't be able to'.

Е́сли всё пойдёт хорошо́, мы смо́жем зако́нчить к пя́тнице.

If all goes well, we'll be able to finish by Friday. — смо́жем, future ability.

Imperative

мочь has no imperative. There is no \моги in normal use — you can't command someone to be able. To tell someone what they may or should do, Russians switch to other words: смоги́ exists only marginally, and the everyday tools are *мо́жешь (a softened "you can / go ahead"), the impersonal мо́жно ("one may / it's allowed"), and попро́буй ("try"). Treat мочь as imperative-less.

Participles and verbal adverbs

Form	Russian	Note
present active participle	могу́щий	"(the one) able" — (literary / rare)
verbal adverb	—	no normal verbal adverb in use
past active participle	мо́гший	(literary / rare)

Both participles are (literary) and uncommon; мочь has no everyday verbal adverb. You will essentially never need to produce these — recognise them in older prose and move on.

Key uses & collocations

1. мочь + infinitive — possibility and power

The core meaning. мочь + an infinitive = "to be physically/circumstantially able to do X" — the door isn't blocked, you have the time, the strength, the opportunity.

Я могу́ тебя́ подвезти́, мне всё равно́ по доро́ге.

I can give you a lift, it's on my way anyway. — circumstantial ability.

2. мочь vs уме́ть — possibility vs acquired skill

This is the distinction English "can" hides. мочь = it's possible right now / I have the power. уме́ть = I have the learned skill / know how to do it (swimming, driving, a language). "I can swim" as a skill is Я уме́ю пла́вать; "I can swim today, the pool is open" is Я могу́ пла́вать сего́дня.

Я уме́ю води́ть маши́ну, но сего́дня не могу́ — вы́пил вина́.

I know how to drive (skill = уме́ю), but today I can't (= не могу́) — I've had wine. Both 'can' in English, split in Russian.

Он уме́ет игра́ть на гита́ре.

He can play the guitar (he has the skill). — уме́ть, not мочь, for a learned ability.

The full contrast is laid out on the мочь vs уме́ть page.

3. мо́жешь / мо́жно — permission and polite requests

мо́жешь / мо́жете + infinitive is a soft way to grant or ask permission ("you can / may"). For impersonal permission ("may one?"), Russian uses мо́жно + infinitive, with the dative for the person.

Мо́жешь взять мою́ маши́ну, е́сли ну́жно.

You can take my car if you need to. — мо́жешь = granting permission.

Мо́жно мне сесть здесь?

May I sit here? — impersonal мо́жно + dative мне. The everyday way to ask permission.

The permission family (мо́жно / нельзя́ / dative + modals) is detailed on the permission requests and impersonal modals pages.

4. Past and future ability — мог / смог

Use the past мог/могла́ for ongoing ability or "could (was able)," and the perfective смог/смогла́ for "managed to" — a single successful outcome. Ability across tenses is covered on the ability in past and future page.

Я до́лго не мог реши́ть э́ту зада́чу, но в конце́ концо́в смог.

I couldn't solve this problem for a long time, but in the end I managed (to). — не мог (ongoing inability) vs смог (a single success).

Common Mistakes

❌ Я можу́. / Я мо́жу.

Incorrect — the я form has г: могу́. The ж appears only in мо́жешь–мо́жете.

✅ Я могу́.

I can.

❌ Он мочи́л прийти́. / Он мо́гл.

Incorrect — the masculine past has no -л and no -ил: it's bare мог. (Feminine могла́.)

✅ Он не мог прийти́.

He couldn't come.

❌ Я могу́ говори́ть по-ру́сски. (meaning 'I have the skill')

Wrong verb for a learned skill — use уме́ть: Я уме́ю говори́ть по-ру́сски. мочь is for circumstantial possibility.

✅ Я уме́ю говори́ть по-ру́сски.

I can (know how to) speak Russian.

❌ Моги́ сде́лать э́то! (as a command)

Incorrect — мочь has no imperative. Say it another way: Сде́лай э́то (just the action), or Ты мо́жешь сде́лать э́то.

✅ Ты мо́жешь э́то сде́лать.

You can do this.

❌ За́втра я бу́ду мочь прийти́.

Awkward — future 'can' uses the perfective смочь: За́втра я смогу́ прийти́.

✅ За́втра я смогу́ прийти́.

Tomorrow I'll be able to come.

Key Takeaways

Present: г/ж alternation — могу́ (г) / мо́жешь / мо́жет / мо́жем / мо́жете (ж) / мо́гут (g again). End-stress only in могу́.
Past: no masculine -л — мог / могла́ / могло́ / могли́ (feminine, neuter, plural end-stressed).
No imperative — use мо́жешь / мо́жно / a plain command instead.
Future is carried by the perfective смочь (смогу́, смо́жешь … смо́гут; past смог/смогла́) = "to manage to."
мочь vs уме́ть: мочь = possibility / power right now; уме́ть = a learned skill (driving, swimming, a language). English "can" covers both — Russian doesn't.
мог бы = polite conditional "could / could have"; мо́жешь / мо́жно = permission.

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