An Esperanto infinitive ends in -i: iri “to go,” legi “to read,” esti “to be.” It can complete the meaning of another verb, much as an English infinitive or -ing form does in “want to leave,” “can swim,” and “enjoy reading.” The finite main verb carries tense or mood; the infinitive names the dependent action without giving it a separate tense or grammatical subject.
What the -i form does
The infinitive presents the general idea of an action or state. It does not mark present, past, future, conditional, or volitive meaning, and it never agrees with person or number.
| Ending | Function | Example |
|---|---|---|
| -i | infinitive, neutral for time and mood | legi — to read |
| -as | present reality | legas — read(s), is reading |
| -is | past reality | legis — read, was reading |
| -os | future reality | legos — will read |
| -us | imagined or conditional | legus — would read |
| -u | willed, requested, or purposed | legu — read!, should read |
In a complement construction, select a finite ending for the main verb and -i for the dependent action:
Mi volas legi tiun romanon.
I want to read that novel.
Ni komencos labori je la oka.
We'll start working at eight.
The present volas locates the desire now; the future komencos locates the beginning later. Legi and labori do not need their own tense because their time is interpreted through the main verb and context.
The understood subject
An infinitive does not take an ordinary grammatical subject directly. You cannot say mi legi inside a sentence as though legi were finite. Instead, its performer is understood from the construction.
With many common complement-taking verbs, the main-clause subject also performs the infinitive action:
Sara decidis resti hejme.
Sara decided to stay home.
La gastoj esperas alveni antaŭ la vespermanĝo.
The guests hope to arrive before dinner.
Sara both decides and stays; the guests both hope and arrive. This same-subject relation is obligatory with povi, devi, and voli followed directly by an infinitive.
Mi povas helpi post la tagmanĝo, sed mi devas foriri je la kvina.
I can help after lunch, but I have to leave at five.
If a different person is to perform the desired action, Esperanto commonly uses a finite ke-clause instead:
Mi volas, ke vi legu la dokumenton.
I want you to read the document.
Compare Mi volas legi la dokumenton, where mi must be the reader. English allows “I want you to read” with an object-like you before the infinitive; Esperanto does not copy that pattern with voli.
Some verbs of influence and perception allow another participant to supply the infinitive's understood subject, as in Mi helpis ŝin porti la valizon. Those patterns depend on the main verb's valency and belong on Subject Control with Infinitives. The reliable beginner rule is to learn the complement pattern together with each main verb.
Which verbs take an infinitive complement?
Common groups include:
| Meaning | Common verbs | Example pattern |
|---|---|---|
| modality | povi, devi, voli | povas veni |
| beginning and ending | komenci, ĉesi, fini | ĉesis pluvi |
| intention and decision | intenci, decidi, plani | decidis resti |
| attempt and success | provi, sukcesi | provis malfermi |
| attitude | ŝati, preferi, timi | ŝatas danci |
| memory and commitment | memori, forgesi, promesi | promesis telefoni |
Ĉu vi ĉiam memoras malŝalti la fornon antaŭ ol vi foriras?
Do you always remember to turn off the oven before you leave?
Mi provis malfermi la fenestron, sed ĝi estis blokita.
I tried to open the window, but it was stuck.
Ŝi ĉesis trinki kafon vespere, ĉar ĝi malhelpis ŝin dormi.
She stopped drinking coffee in the evening because it kept her from sleeping.
There is no fully mechanical rule that predicts every verb's complement pattern. This is an honest lexical learning task: learn decidi fari, promesi fari, and insisti, ke iu faru as patterns, just as English learners must learn which verbs take to and which take -ing. Esperanto is highly regular in its verb endings, but valency still belongs partly to individual words.
Infinitives remain verbs inside the phrase
Although an infinitive phrase can complete another verb much like a noun phrase, the infinitive itself remains verbal. It can take a direct object, adverbs, and prepositional complements.
Ni planas zorge kontroli ĉiujn ciferojn antaŭ la publikigo.
We plan to check all the figures carefully before publication.
In zorge kontroli ĉiujn ciferojn, zorge modifies kontroli, and ĉiujn ciferojn is its direct object. The accusative belongs on the object, not on the infinitive. Esperanto infinitives never take -n.
Petro promesis paroli kun la posedanto pri la liko.
Petro promised to speak with the owner about the leak.
The prepositional frames paroli kun iu and paroli pri io remain intact inside the complement. A change from promesis to promesos changes the time of the promise, not the valency of paroli.
Objects may sometimes be placed before an infinitive, but proximity makes structure easier to read. Mi promesis rapide sendi la dokumentojn al ŝi clearly groups the manner, action, object, and recipient. Esperanto's flexible order is not a reason to separate related words without purpose.
Negating the main verb or the infinitive
Place ne before the element whose meaning is denied. Negating the main verb and negating the dependent action can produce different meanings.
Mi ne decidis foriri.
I did not decide to leave.
Mi decidis ne foriri.
I decided not to leave.
In the first sentence, no decision to leave occurred; another decision may or may not have been made. In the second, there was a decision, and its content was nondeparture.
The contrast is especially clear with povi:
Li ne povas ĉeesti.
He cannot attend.
Li povas ne ĉeesti.
He has the option not to attend.
The written position of ne carries real scope. Do not automatically place it before the first verb just because English often does.
More than one infinitive
An infinitive can itself take another infinitive complement, creating a transparent chain.
Mi volas provi lerni ludi la gitaron.
I want to try to learn to play the guitar.
The finite volas supplies present time. Provi, lerni, and ludi successively name dependent actions. The sentence is grammatical, but long chains can be hard to process. In polished (formal) prose, divide a chain or replace part of it with a noun or clause when the relationships stop being immediately clear.
Infinitive complements versus ke-clauses
An infinitive compresses an action whose subject is recoverable. A ke-clause has its own finite verb and can express its own subject and time or mood more explicitly.
Mi esperas reveni antaŭ vendredo.
I hope to return before Friday.
Mi esperas, ke Ana revenos antaŭ vendredo.
I hope that Ana will return before Friday.
The first makes mi the returner. The second introduces Ana and explicitly marks her return as future with -os. After verbs of hope, thought, knowledge, and reporting, a ke-clause may also be chosen when a full proposition is more important than a compact same-subject action.
Infinitives can have other functions—as subjects, after certain prepositions, and in labels or instructions—but those are not complement uses. See Infinitive Subjects and Infinitives after Prepositions for those structures.
Common Mistakes
Making the complement finite
❌ Mi volas iras hejmen.
Incorrect — the dependent action must use -i.
✅ Mi volas iri hejmen.
I want to go home.
Adding English to as a preposition
❌ Ni decidis al resti unu plian nokton.
Incorrect — the -i ending itself marks the infinitive; no al is added.
✅ Ni decidis resti unu plian nokton.
We decided to stay one more night.
Giving the infinitive accusative -n
❌ Ŝi ŝatas legin antaŭ ol dormi.
Incorrect — an infinitive never takes accusative -n.
✅ Ŝi ŝatas legi antaŭ ol dormi.
She likes reading before going to sleep.
Copying an English different-subject infinitive
❌ Mi volas lin telefoni hodiaŭ.
Incorrect — voli plus an infinitive requires the same subject.
✅ Mi volas, ke li telefonu hodiaŭ.
I want him to call today.
Adding esti as an auxiliary
❌ Ili estas planas vojaĝi somere.
Incorrect — planas is already the finite verb.
✅ Ili planas vojaĝi somere.
They plan to travel in the summer.
Key Takeaways
- An -i form has no person, number, tense, or mood; the finite main verb supplies the frame.
- The main subject normally supplies the infinitive's understood subject, and povi/devi/voli + infinitive require that shared subject.
- The infinitive remains a verb and keeps its own objects, adverbs, and prepositional complements.
- Use ne next to the verb whose meaning you negate, and use a ke-clause when a different explicit subject is needed.
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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.
- Infinitives after Modal VerbsA1 — Combine povi, devi, and voli with a same-subject infinitive while keeping tense, mood, objects, and negation in the right layer.
- Subject Control with InfinitivesA2 — Identify the understood actor of an infinitive after same-subject, influence, perception, causative, and purpose constructions.
- Infinitive SubjectsA1 — Use an infinitive phrase as a clause subject, describe its action with an adverb, and identify its understood actor clearly.
- Infinitives after PrepositionsA2 — Choose the established preposition-plus-infinitive patterns and replace disfavored combinations with clauses, participles, or action nouns.
- Ke-ClausesA2 — How finite clauses introduced by ke function as statements, subjects, objects, complements, and content descriptions.