a trebui — must, to have to | Romanian Grammar

A trebui means must or to have to — it is the workhorse verb for expressing obligation and necessity, and one of the first verbs you will reach for in real conversation. It is also unusual: in the standard modern language it is impersonal and defective, meaning it does not conjugate for person the way ordinary verbs do. The present tense has a single, frozen form — trebuie — that you use no matter who the subject is. There is no eu trebuiesc, no noi trebuim; those forms simply do not exist in careful modern Romanian.

Because it is a modal of necessity, a trebui is almost always followed by a subjunctive clause with să (trebuie să plec — "I have to leave") or, in impersonal statements, by a noun (trebuie timp — "it takes time"). This page lays out every tense honestly: where the verb is genuinely invariable, the table says so; where it borrows the bare 3rd-person form, you will see it used impersonally rather than padded out with invented personal endings.

Prezent indicativ

This is the heart of the verb and the single most important thing to internalize: trebuie is invariable. The same word does the job for eu, tu, el, noi, voi, and ei alike. What changes is the verb inside the să-clause, which carries the real person.

Person	Form (invariable)	With să-clause
eu	trebuie	trebuie să plec
tu	trebuie	trebuie să pleci
el / ea	trebuie	trebuie să plece
noi	trebuie	trebuie să plecăm
voi	trebuie	trebuie să plecați
ei / ele	trebuie	trebuie să plece

Trebuie să plec, am întârziat deja.

I have to go, I'm already late.

Voi trebuie să terminați raportul până vineri.

You all have to finish the report by Friday.

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Say it out loud: eu trebuie, tu trebuie, noi trebuie — one word for everyone. The form trebuiesc exists only as a colloquial, non-standard plural for the "I need (things)" meaning (see below) and is best avoided in writing.

Imperfect

The imperfect has one normal-looking form, trebuia, again used impersonally for any subject. This form is enormously useful because trebuia să is the standard way to say should have / was supposed to — an unfulfilled past obligation.

Person	Form (invariable)	With să-clause
eu	trebuia	trebuia să plec
tu	trebuia	trebuia să pleci
el / ea	trebuia	trebuia să plece
noi	trebuia	trebuia să plecăm
voi	trebuia	trebuia să plecați
ei / ele	trebuia	trebuia să plece

Trebuia să-l sun ieri, dar am uitat complet.

I should have called him yesterday, but I completely forgot.

Trebuia să fim acolo la opt, nu la nouă.

We were supposed to be there at eight, not nine.

Perfect compus

For a completed past obligation that was in fact fulfilled, Romanian uses a trebuit, the impersonal compound past (auxiliary a + participle trebuit). Note the contrast with the imperfect: a trebuit să = "had to (and did)," while trebuia să = "was supposed to / should have (often didn't)."

Person	Form (impersonal)
any subject	a trebuit (să …)

A trebuit să iau un taxi, că pierdusem ultimul tren.

I had to take a taxi, because I'd missed the last train.

Ne pare rău, dar a trebuit să anulăm întâlnirea.

We're sorry, but we had to cancel the meeting.

Mai-mult-ca-perfectul

The synthetic pluperfect is trebuise, again impersonal. It is rare in speech but appears in narrative prose to mark an obligation that pre-dated another past event.

Person	Form (impersonal)
any subject	trebuise (să …)

Înțelesese, în sfârșit, de ce trebuise să mintă.

He had finally understood why he had had to lie.

Viitor

Future obligation uses the invariable va trebui (formal voi-future) or o să trebuiască (colloquial). The conjunctive form inside the colloquial future is trebuiască — the one place a person-like ending surfaces, but it is still impersonal 3rd person.

Register	Form (impersonal)
Viitor (formal)	va trebui (să …)
Colloquial (o să)	o să trebuiască (să …)

Va trebui să vorbim despre asta mai târziu.

We'll have to talk about this later.

O să trebuiască să-ți iei concediu pentru mutare.

You'll have to take time off for the move.

Conjunctiv prezent

Used after another verb or impersonally, the subjunctive form is (să) trebuiască. In everyday speech this is uncommon, since obligation is usually expressed with the indicative trebuie; it shows up mainly inside other modal frames.

Person	Form (impersonal)
any subject	să trebuiască

Nu vreau să trebuiască să te rog de două ori.

I don't want it to be necessary to ask you twice.

Condițional prezent

The conditional is ar trebui, the single most useful polite/advice form of the whole verb: ar trebui să = should (soft recommendation). It is invariable; the person lives in the să-clause.

Person	Form (invariable)	With să-clause
eu	ar trebui	ar trebui să plec
tu	ar trebui	ar trebui să pleci
el / ea	ar trebui	ar trebui să plece
noi	ar trebui	ar trebui să plecăm
voi	ar trebui	ar trebui să plecați
ei / ele	ar trebui	ar trebui să plece

Ar trebui să te odihnești, arăți obosit.

You should rest, you look tired.

Imperativ

A trebui has no imperative. You cannot command necessity itself. To tell someone they must do something, you use trebuie să + subjunctive, or you simply give the bare command of the other verb.

	Form
tu / voi	— (does not exist)

Forme nepersonale

The verb is defective here too: in standard modern usage there is no living gerund or supine. The infinitive and participle are the forms you will meet.

Form	Romanian
Infinitiv	(a) trebui
Gerunziu	trebuind (rare/literary)
Participiu	trebuit
Supin	— (not used)

Usage

Beyond pure obligation, a trebui has a second, fully personal life: the construction îmi trebuie + noun = I need (something). Here the thing needed is the grammatical subject and the person is a dative clitic (îmi, îți, îi, ne, vă, le), so the verb agrees with the noun: îmi trebuie timp (sg.), îmi trebuie două ouă (pl., trebuie still, since ouă is the subject).

Îmi trebuie timp ca să mă gândesc bine.

I need time to think it over properly.

Ne trebuie încă două scaune pentru cină.

We need two more chairs for dinner.

Cât crezi că trebuie să aștept la coadă?

How long do you think I have to wait in line?

Trebuie multă răbdare ca să crești copii.

It takes a lot of patience to raise children.

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The biggest payoff on this whole page is the imperfect trebuia să = should have / was supposed to. English needs a heavy "should have + past participle" structure; Romanian gets there with one simple imperfect: Trebuia să-mi spui = "You should have told me." Drill this — it is everywhere in real speech.

Source-language note for English speakers

English "must" is also defective — there is no to must, no musted — so the idea of a verb with missing forms should feel familiar. The trap is different: English speakers instinctively try to make the person visible on the verb, producing things like we musts or, transferring to Romanian, noi trebuim. Resist this. In Romanian the obligation word stays frozen as trebuie and the person is expressed entirely inside the să-clause that follows. Treat trebuie the way you treat English "it is necessary": one fixed shape, with the real action and its subject living in the clause after it.

Common Mistakes

❌ Noi trebuim să plecăm.

Incorrect — trebui does not conjugate for person; there is no trebuim.

✅ Noi trebuie să plecăm.

We have to leave.

❌ Eu trebuiesc să învăț.

Incorrect — trebuiesc is not a standard verb form here.

✅ Eu trebuie să învăț.

I have to study.

❌ Trebuia că-l sun ieri.

Incorrect — necessity takes a să-clause, not a că-clause.

✅ Trebuia să-l sun ieri.

I should have called him yesterday.

❌ Îmi trebuie de timp.

Incorrect — the noun is the bare subject; no preposition de.

✅ Îmi trebuie timp.

I need time.

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