Needs and Obligations | Esperanto Grammar

English uses need, have to, must, should, and be required to across several kinds of necessity. Esperanto distributes those meanings among frames with different subjects and different scopes. Bezoni profiles a need, necesi presents a situation as necessary, and devi presents an action or state as more or less unavoidable for its subject.

These meanings overlap, but their grammar is not interchangeable. The crucial questions are: who has the need, who must act, what creates the pressure, and does negation cancel the obligation or prohibit the action?

Bezoni: a person or situation lacks something

For a needed thing, use bezoni + accusative object. The variable slot can name a resource, person, change, or result.

Ni bezonas pli da tempo por kontroli la lastajn ciferojn.

We need more time to check the final figures.

La malnova tegmento bezonas urĝan riparon antaŭ la vintro.

The old roof needs urgent repair before winter.

For an action performed by the same subject, use bezoni + infinitive. This often expresses a practical, bodily, or situational requirement rather than an externally imposed duty.

Mi bezonas ripozi post la vojaĝo; ni povas paroli morgaŭ.

I need to rest after the trip; we can talk tomorrow.

La motoro bezonas malvarmiĝi antaŭ ol ni daŭrigos.

The engine needs to cool down before we continue.

If another participant must produce the needed result, use a ke-clause with volitive -u:

Mi bezonas, ke vi sendu la originalan dosieron, ne foton de la ekrano.

I need you to send the original file, not a photo of the screen.

The ke-clause is not an assertion that the person already acts. It identifies the desired or required outcome, which is why sendu is appropriate. A passive alternative can keep the affected item as subject: La dosiero bezonas esti sendita hodiaŭ.

The wider system behind this choice is explained under the volitive in subordinate clauses.

The noun frame is different: havi bezonon de io. The preposition belongs to bezono, not to verbal bezoni.

Post tri horoj da diskutado ĉiuj havis bezonon de paŭzo.

After three hours of discussion, everyone needed a break.

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Keep the frames distinct: bezoni ion, but havi bezonon de io. English “need of” must not insert de after the verb.

Devi + infinitive: the subject cannot reasonably avoid the action

Devi normally takes an infinitive whose understood subject is the same as the subject of devi. The pressure may come from rules, circumstances, another person's will, morality, or simple inevitability; context supplies the source.

Ĉiuj vizitantoj devas montri identigilon ĉe la enirejo.

All visitors must show identification at the entrance.

La lasta buso ne venis, do ni devis marŝi hejmen.

The last bus did not come, so we had to walk home.

Mi devas fini ĉi tiun raporton antaŭ la kunveno je la naŭa.

I have to finish this report before the meeting at nine.

The same surface frame can express distinct sources of necessity. Add the source when it matters: laŭ la kontrakto, pro la vetero, ĉar la estro tion postulis, or por eviti danĝeron. Devi itself does not encode whether the duty is legal, moral, practical, or personal.

To emphasize external compulsion, use esti devigita + infinitive. This is stronger than neutral devi and often implies that the subject did not freely choose the action.

Pro la inundo la organizantoj estis devigitaj nuligi la koncerton.

Because of the flood, the organizers were forced to cancel the concert.

In (formal/administrative) language, esti postulata and oni postulas, ke … -u identify an explicit requirement. They should not replace every everyday devas.

Impersonal necessity with necesas

Necesas + infinitive evaluates an action as necessary without naming an obligated subject in the main clause. An explicit al-phrase can identify for whom the necessity holds, but speakers often choose a personal devi sentence instead.

Necesas konservi kopion de ĉiuj subskribitaj dokumentoj.

It is necessary to keep a copy of all signed documents.

Por atingi la vilaĝon antaŭ mallumo, necesas foriri nun.

To reach the village before dark, it is necessary to leave now.

When the necessary outcome has its own subject, use necesas, ke … -u or estas necese, ke … -u.

Necesas, ke ĉiuj aliĝintoj konfirmu sian ĉeeston ĝis Vendredo.

It is necessary for everyone registered to confirm their attendance by Friday.

The shorter verb necesas and the adjective frame estas necese are both standard. The former is concise; the latter can carry explicit tense or modality more visibly: Estus necese ŝanĝi la planon. Neither structure says who issued an order unless the context adds that information.

Compare the focus:

Frame	What it foregrounds	Natural use
Ni bezonas foriri.	our need	Our situation calls for departure.
Ni devas foriri.	our unavoidable obligation	We have to leave.
Necesas foriri.	necessity of the action	Leaving is necessary.

The differences are perspectival, not mathematical. In an emergency all three may describe the same required departure, but they package the reason differently.

Recommendations with devus

Devus is the conditional of devi. It often gives advice or states an obligation whose fulfillment is uncertain: English “should” is a frequent translation.

Vi devus sekurkopii la dosierojn antaŭ ol instali la novan version.

You should back up the files before installing the new version.

La pako devus alveni morgaŭ, se ne estos plia prokrasto.

The package should arrive tomorrow if there is no further delay.

The second example is an expectation, not advice to the package. Context distinguishes a recommended action from a predicted result. For gentler advice in conversation, estus bone… can reduce the force: Estus bone, se vi antaŭe telefonus.

Inferential devi: “must be”

Devi also expresses a strong conclusion from evidence. No authority obliges the subject; the speaker judges the proposition highly likely or inevitable.

La lumoj estas ŝaltitaj; ili devas esti ankoraŭ en la oficejo.

The lights are on; they must still be in the office.

Ŝi ne respondas, do ŝia telefono devas esti sen kurento.

She is not answering, so her phone must be out of power.

This epistemic use is standard and well established. It can be ambiguous without context: Li devas labori may mean that he is required to work or that evidence leads the speaker to conclude he is working. Add the grounds or choose certe/verŝajne when the distinction matters.

Negation: no obligation is not prohibition

This is the genuinely difficult part. Logically, ne devi fari should cancel the obligation, while devi ne fari should require non-action. Historical and present usage, however, has also used ne devas fari for prohibition. Spoken stress may disambiguate it, but writing lacks that signal.

For clear international prose, use these explicit frames:

Intended meaning	Recommended wording
there is no need or duty	ne bezonas fari / ne estas necese fari
the action is forbidden	ne rajtas fari / estas malpermesite fari
non-action is required	devas ne fari, if the logical contrast is explicitly important

— Ĉu mi devas resti ĝis la fino? — Ne, vi ne bezonas resti, se vi jam finis vian parton.

— Must I stay until the end? — No, you do not need to stay if you have finished your part.

Vizitantoj ne rajtas foti en ĉi tiu ĉambro.

Visitors must not take photographs in this room.

The ambiguity of ne devas is an attested usage fact, not a license to be unclear. Foundational word order places ne before what it negates; historical convention complicates this one modal combination. The best editorial practice is to write the intended meaning explicitly.

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For English “don't have to,” choose ne bezonas. For “must not,” choose ne rajtas or estas malpermesite. Those forms remain clear without relying on stress.

Compact obligation words and register

The suffix -end- creates adjectives meaning “that must be done”: pagenda fakturo, solvenda problemo, legenda dokumento. These are productive and precise, especially in (formal/technical) writing, but a long stack can sound bureaucratic. Conversation often prefers fakturo, kiun oni devas pagi.

Nepre means that something is indispensable, certain, or emphatically required by the context: Vi nepre venu “Do come / you absolutely must come.” It intensifies the necessity but is not itself a verb selecting an infinitive.

La kandidatiĝo estas sendenda elektronike, sed la originaloj nepre restu ĉe vi.

The application must be sent electronically, but be sure to keep the originals.

Neutral speech favors bezoni, devi, and direct volitives. Administrative prose may use estas postulite, estas devige, and -enda forms. Good C1 style does not maximize formality; it names the source and scope of obligation accurately.

Common Mistakes

Adding de after verbal bezoni

❌ Mi bezonas de nova adaptilo.

Incorrect — bezoni takes a direct object.

✅ Mi bezonas novan adaptilon.

I need a new adapter.

Giving devi a noun object

❌ Ni devas pli da mono por fini la riparon.

Incorrect — devi normally takes an action infinitive, not the needed resource.

✅ Ni bezonas pli da mono por fini la riparon.

We need more money to finish the repair.

Hiding a different subject inside an infinitive

❌ Mi bezonas vi sendi la fakturon hodiaŭ.

Incorrect — a different actor needs an explicit ke-clause.

✅ Mi bezonas, ke vi sendu la fakturon hodiaŭ.

I need you to send the invoice today.

Using an ambiguous negative for “do not have to”

❌ Vi ne devas veni morgaŭ.

Ambiguous — this can be understood as either no obligation or a prohibition.

✅ Vi ne bezonas veni morgaŭ.

You do not need to come tomorrow.

Translating “must not” as mere absence of need

❌ Vi ne bezonas eniri; estas danĝere.

Wrong if entry is forbidden rather than merely unnecessary.

✅ Vi ne rajtas eniri; estas danĝere.

You must not enter; it is dangerous.

Key Takeaways

Use bezoni for a needed thing or same-subject action, necesas to evaluate an action impersonally, and devi for an unavoidable action or strong inference. Use a volitive ke-clause when a separate participant must act. In negative contexts, replace potentially ambiguous ne devas with explicit ne bezonas for absence of obligation and ne rajtas/estas malpermesite for prohibition.

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