The modal verbs povi “can/be able,” devi “must/have to,” and voli “want/intend” normally take an infinitive in -i. The modal carries tense or mood; the infinitive names the possible, necessary, or desired action. Both verbs have the same understood subject.
The core pattern
Build the construction as subject + finite modal + infinitive. Esperanto always keeps the infinitive ending -i, even where English uses a bare verb after “can” or “must.”
The finite modal is invariant for person and number: mi povas, ŝi povas, and ili povas. As elsewhere in the verb system, -as, -is, -os, -us, and -u carry tense or mood, while -i marks the dependent infinitive.
| Modal | Core contribution | Example |
|---|---|---|
| povi | ability, circumstantial possibility, or permission | Mi povas veni. |
| devi | obligation, necessity, inevitability, or strong inference | Mi devas veni. |
| voli | desire or intention | Mi volas veni. |
Hodiaŭ mi povas renkonti vin antaŭ la kunveno.
Today I can meet you before the meeting.
Ni devas fini la raporton antaŭ vendredo.
We have to finish the report before Friday.
La infanoj volas ludi ekstere.
The children want to play outside.
The modal and infinitive form a tight complex predicate. In ni devas fini la raporton, ni is the subject of both devas and fini, while la raporton is the object required by fini.
The subject is necessarily shared
With these three verbs, the subject of the modal performs the infinitive action.
Sara volas telefoni al la hotelo.
Sara wants to call the hotel.
Sara both wants and calls. If someone else is supposed to perform the action, use a finite ke-clause, normally with volitive -u after voli.
Sara volas, ke Leo telefonu al la hotelo.
Sara wants Leo to call the hotel.
English says “Sara wants Leo to call,” using an object plus infinitive. Esperanto does not copy that construction after voli. The contrast is systematic:
Mi volas foriri nun.
I want to leave now. (I leave)
Mi volas, ke vi foriru nun.
I want you to leave now. (you leave)
The subject control with infinitives page explains same-subject and different-subject patterns across more verb classes.
The modal carries tense and mood
The infinitive itself has no tense. Change the modal ending to locate or frame the whole complex action.
Hieraŭ mi devis labori ĝis malfrue.
Yesterday I had to work late.
Morgaŭ mi povos dormi pli longe.
Tomorrow I will be able to sleep longer.
Mi volus helpi, sed mi ne scias kiel.
I would like to help, but I don't know how.
Bonvolu atendi momenton.
Please wait a moment.
In volus helpi, conditional -us presents the desire politely or hypothetically; helpi stays neutral. Bonvolu is the volitive form of bonvoli and conventionally makes a polite request followed by an infinitive.
Do not mark both verbs for tense. Mi devos laboros is impossible because the dependent action must remain an infinitive.
What povi can mean
Povi covers several meanings that English often divides among “can,” “be able to,” “may,” and circumstantial “be possible.” Context supplies the exact reading.
Post ses monatoj da lernado ŝi jam povas bone konversacii en Esperanto.
After six months of study, she can already converse well in Esperanto. (ability)
La vojo estas denove malfermita, do ni povas iri tra la montoj.
The road is open again, so we can go through the mountains. (circumstances)
Ĉu mi povas uzi vian ŝargilon? — Kompreneble.
May I use your charger? — Of course. (permission)
The same-subject rule holds in every meaning: the person able, permitted, or circumstantially free to act is the doer of the infinitive.
What devi can mean
Devi presents the infinitive action as unavoidable or required. The source may be rules, circumstances, another person's will, or logical inference.
Ĉiuj vizitantoj devas montri identigilon ĉe la enirejo.
All visitors must show identification at the entrance.
La lumo estas ŝaltita; iu devas esti hejme.
The light is on; someone must be at home. (strong inference)
In the second example, nobody imposes an obligation. Devas esti expresses a conclusion presented as practically inevitable. English has the same ambiguity in “must.”
Present devas can also point toward an expected future action, while past devis can describe a past obligation or something scheduled from a past viewpoint.
La trajno devas alveni post kvin minutoj.
The train is supposed to arrive in five minutes.
La ceremonio devis komenciĝi je la deka, sed la ĉefa gasto malfruis.
The ceremony was supposed to begin at ten, but the main guest was late.
These are established uses. The modal meaning, not a special infinitive tense, creates the expectation.
What voli can mean
Voli expresses the subject's desire or intention. The infinitive shows what that same subject wishes to do.
Mi volas lerni kuiri pli bone.
I want to learn to cook better.
— Ĉu vi volas trinki ion? — Jes, mi volas teon.
— Would you like something to drink? — Yes, I'd like tea.
Unlike povi and devi, voli also freely takes an ordinary noun object: mi volas teon. When the desired content is an action performed by someone else, however, use ke ... -u.
Polite questions with voli recognize the addressee's choice. They are ordinary, not especially formal. Bonvolu + infinitive is the conventional concise polite request.
The infinitive controls its own complements
The lexical infinitive decides whether an object or preposition is needed.
Ŝi povas respondi la demandon sen prepariĝo.
She can answer the question without preparation.
Ŝi povas respondi al la kliento morgaŭ.
She can reply to the client tomorrow.
La demandon belongs to transitive respondi in the sense “answer the question”; al la kliento expresses the person replied to. The modal does not erase the verb's valency. Moving the object before the modal is possible because case remains visible: La demandon ŝi povas respondi.
Negation and scope
Ordinarily ne before the modal negates possibility, necessity, or desire.
Mi ne povas veni hodiaŭ.
I cannot come today.
Ŝi ne volas diskuti la aferon nun.
She does not want to discuss the matter now.
Putting ne with the infinitive can contrast the negative action itself.
Vi povas ne partopreni, se vi preferas ripozi.
You may choose not to take part if you would rather rest.
With devi, the logical scope contrast is ne devi fari “not be obliged to do” versus devi ne fari “be obliged not to do.” Actual usage is less tidy: traditional and modern texts also use ne devas for prohibition, while many speakers understand it logically as “does not have to.” When the distinction matters, use ne bezonas for absence of necessity and devas ne, ne rajtas, or a direct negative volitive for prohibition.
Vi ne bezonas veni morgaŭ.
You don't need to come tomorrow.
Vi ne rajtas eniri sen bileto.
You must not enter without a ticket.
These explicit alternatives are the pedagogical recommendation because ne devas can otherwise receive either reading.
Common Mistakes
Dropping the infinitive ending after a modal
❌ Mi povas help vin poste.
Incorrect — Esperanto requires the full infinitive helpi after povas.
✅ Mi povas helpi vin poste.
I can help you later.
Marking both verbs for tense
❌ Ni devos foriros frue.
Incorrect — only the modal carries future -os.
✅ Ni devos foriri frue.
We will have to leave early.
Giving voli + infinitive a different subject
❌ Mi volas vi atendi ekstere.
Incorrect — voli plus an infinitive requires the same subject.
✅ Mi volas, ke vi atendu ekstere.
I want you to wait outside.
Adding esti as an English-style auxiliary
❌ Ŝi estas povas veturi morgaŭ.
Incorrect — povas itself is the finite verb.
✅ Ŝi povas veturi morgaŭ.
She can travel tomorrow.
Using an ordinary noun after povi
❌ Li povas dancadon.
Incorrect — povi takes an infinitive for the possible action.
✅ Li povas danci.
He can dance.
Key Takeaways
- Povi, devi, and voli take an infinitive whose understood subject is the modal's subject.
- The modal carries -as, -is, -os, -us, or -u; the dependent action remains in -i.
- Povi covers ability, circumstances, and permission; devi covers necessity and inference; voli covers desire and intention.
- The infinitive retains its own object and prepositional pattern.
- Use explicit ne bezonas and ne rajtas when the intended scope of negative necessity matters.
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Start learning Esperanto →Related Topics
- The Infinitive in -IA1 — Use the invariant -i form to name an action or state without asserting tense, person, or mood.
- Povi: Can Or Be AbleA2 — Use povi with a same-subject infinitive for ability, circumstances, permission, and possibility, including epistemic and polite readings.
- Devi: Must Or OughtA2 — Use devi for obligation, necessity, expectation, and strong inference, with the right tense, complement, and negative scope.
- Voli: To WantA2 — Use voli with noun objects, same-subject infinitives, and volitive ke-clauses for another person’s desired action.
- Subject Control with InfinitivesA2 — Identify the understood actor of an infinitive after same-subject, influence, perception, causative, and purpose constructions.
- Transitive and Intransitive VerbsA2 — Learn which verbs license a direct object, which require another construction, and how Esperanto systematically changes valency.