This is a paradigm card for moci ("can, to be able to"), but its real job is to show you the pattern behind the famous h/ž wobble — because moci is not a one-off oddity. It is the model verb of a small, closed class: the velar-stem verbs whose infinitive ends in -ci / -ct. Once you see why moci alternates the way it does, the same logic unlocks péci (to bake), téci (to flow), and the prefixed pomoci (to help). For when to choose moci over umět and smět, see the usage page on moci / moct; for the full essential entry, see moci / moct — can. This page is about the machinery.
A 1500-year-old sound change, frozen in one verb
Moci goes back to Proto-Slavic *mogti, with a root ending in the velar consonant g. Two separate sound changes then reshaped it, and modern Czech still wears both:
- g → h everywhere. Czech (and Slovak) turned every old g into h. This is why Czech has mohu where Polish still says mogę. You see the surviving h in the bookish present mohu, mohou and right through the past tense mohl.
- g → ž before a front vowel. In the middle present forms, the ending began with a front vowel (-eš, -e, -eme, -ete), which triggered the First Slavic Palatalization — the change that softens velars to postalveolars: k → č, g → ž, ch → š. So *mož-e- gave může. The first and third plural, by contrast, had back/nasal vowel endings that didn't trigger palatalization, so their velar stayed put as h (mohu, mohou).
That levelling is the colloquial layer. Everyday spoken Czech disliked having two stems in one paradigm, so it spread the ž outward into the já and oni slots, giving můžu, můžou. The older mohu, mohou survive in writing and formal speech.
The present tense — two registers
| Person | Literary (formal) | Spoken (informal) | Meaning |
|---|---|---|---|
| já | mohu | můžu | I can |
| ty | můžeš | můžeš | you can (sg.) |
| on / ona / ono | může | může | he / she / it can |
| my | můžeme | můžeme | we can |
| vy | můžete | můžete | you can (pl./formal) |
| oni / ony / ona | mohou | můžou | they can |
The split touches only the corners — mohu/můžu and mohou/můžou. The four middle forms (můžeš, může, můžeme, můžete) are identical in both registers, always with ž and the ring vowel ů.
Mohu vás na chvíli vyrušit?
May I disturb you for a moment? (literary, e.g. knocking on a manager's door)
Hele, můžu tě na chvíli vyrušit?
Hey, can I bug you for a sec? (colloquial, same meaning)
Promiň, teď opravdu nemůžu mluvit, zavolám ti později.
Sorry, I really can't talk right now, I'll call you later.
Negation is the prefix ne-: spoken nemůžu, nemůžeš … nemůžou; literary nemohu … nemohou.
The whole class, side by side
Here is the payoff. Three verbs run the velar alternation in the present in exactly the same shape — the velar surviving at the back-vowel edges (literary) and palatalizing before -e-. Only the consonant differs, because the underlying velar differs: moci had g (→ h/ž), while péci and téci had k (→ k/č).
| Form | moci (g → h/ž) | péci (k → k/č) | téci (k → k/č) |
|---|---|---|---|
| infinitive | moci / moct | péci / péct | téci / téct |
| já (lit. / coll.) | mohu / můžu | peku / peču | teku / teču |
| on / ona | může | peče | teče |
| oni (lit. / coll.) | mohou / můžou | pekou / pečou | tekou / tečou |
| past (m.) | mohl | pekl | tekl |
Babička dnes peče vánočku, voní to po celém bytě.
Grandma is baking a sweet braided loaf today, the whole flat smells of it.
Z kohoutku pořád teče voda, musíme zavolat instalatéra.
Water keeps running from the tap, we have to call a plumber.
The fourth member, říci / říct ("to say"), belongs to the same -ci infinitive family and shares the velar root (you hear the k in řekni, řekl), but it is the cousin, not the twin: its present-future is built with an inserted -ne- — řeknu, řekneš, řekne, řeknou — so it does not show the h/ž or k/č present alternation. Keep it filed nearby but conjugate it separately (see říci / říct).
Řekni mi pravdu, prosím tě.
Tell me the truth, please. (říci — note the řek- root, not a present alternation)
The past tense
The past reverts cleanly to the h-stem and forms the l-participle. The cluster takes no helping vowel: it is mohl, never *mohel. (Compare the parallel pekl, tekl, řekl.)
| Subject | Participle | First-person example |
|---|---|---|
| masc. sg. | mohl | mohl jsem (I could / was able to) |
| fem. sg. | mohla | mohla jsem |
| neut. sg. | mohlo | mohlo |
| masc. anim. pl. | mohli | mohli jsme |
| fem. / neut. pl. | mohly / mohla | mohly jsme |
Nemohl jsem dnes přijít dřív, ujel mi autobus.
I couldn't come earlier today, I missed the bus. (male speaker)
Mohli jsme to stihnout, kdybychom vyrazili o hodinu dřív.
We could have made it if we'd set off an hour earlier.
The future tense
Moci is imperfective, so the future is the analytic budu-future, built on the literary infinitive moci: budu moci, budeš moci … budou moci. In speech you will also hear budu moct; both are fine.
Až se uzdravím, budu zase moci běhat.
Once I get better, I'll be able to run again.
The imperative is, in practice, avoided — telling someone "be able to!" makes little sense. (The prefixed pomoci does have a live imperative, pomoz!; see pomáhat / pomoci.)
The conditional — the polite request
The conditional joins the h-participle with the conditional auxiliary bych / bys / by / bychom / byste / by. This is the everyday formula for a courteous request — softer and more natural than a blunt Můžeš?. The participle agrees with the person you address.
Mohl byste mi prosím pomoct s tím kufrem?
Could you please help me with that suitcase? (to a man, formally)
Mohla bys mi na chvilku půjčit nabíječku?
Could you lend me your charger for a moment? (to a woman, informally)
Common mistakes
❌ Včera jsem mohel přijít.
Incorrect — the masculine participle is the bare cluster mohl, with no inserted vowel.
✅ Včera jsem mohl přijít.
Yesterday I could have come. (male speaker)
❌ Oni možou počkat.
Incorrect spelling — the colloquial 3rd plural is můžou, with ů and ž.
✅ Oni můžou počkat.
They can wait.
❌ Babička dneska peku buchty.
Wrong person — peku is the 'I' form; 'grandma bakes' is the 3rd-person peče.
✅ Babička dneska peče buchty.
Grandma is baking buns today.
❌ Budu můžu přijít později.
Incorrect — the future uses the infinitive (budu moci), never a finite present form.
✅ Budu moci přijít později.
I'll be able to come later.
Key takeaways
- Moci is the model velar-stem -ci/-ct verb: the old velar softens to ž before -e- (middle present) and survives as h before back vowels (edges, past, infinitive).
- Present: literary mohu … mohou, spoken můžu … můžou; the middle four (můžeš, může, můžeme, můžete) are shared.
- The same pattern runs through péci (peku/peču) and téci (teku/teču) with k/č; říci shares the -ci infinitive but takes a -ne- present (řeknu).
- Past is the bare cluster mohl (not mohel), parallel to pekl, tekl; future budu moci; conditional Mohl/Mohla byste …? = the polite "Could you …?".
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Start learning Czech→Related Topics
- moci / moct — can, to be able toA1 — Full conjugation of the modal verb moci/moct (can), its h/ž stem alternation, the literary versus colloquial forms, and how it differs from umět and smět.
- moci / moct — Can, May, Be AbleA2 — The three modal senses of moci/moct — ability, possibility, and permission — and how 'can' splits across moci, umět, and smět.
- péci / péct — to bake, to roastB1 — Full conjugation of péci/péct, a Class I verb with c/č/k velar alternation.
- říci / říct — to say, to tellA1 — Full conjugation of perfective říci/říct and its imperfective partner říkat, with dative-addressee government and the infinitive-vs-present-stem mismatch.
- pomáhat / pomoci — to helpA2 — Side-by-side conjugation of pomáhat (imperfective) and pomoci (perfective), the dative of the person helped, and the s + instrumental of the task.