You already know trebuie să — Romanian's blunt "must / have to." This page is about its softer twin. When English moves from "you must go" to "you should go," it swaps one modal for another. Romanian does something more elegant and more systematic: it puts the very same verb a trebui into the conditional, giving ar trebui să. "Should" and "ought to" are not separate words in Romanian — they are trebuie stepped back from fact into the hypothetical. Internalise that one move and the whole field of advice-giving opens up, including the past "should have," which simply stacks the conditional one layer deeper.
The core insight: should = the conditional of must
Trebuie să pleci states a hard obligation: "you have to leave," no room for negotiation. Drop the verb into the conditional — ar trebui să pleci — and the obligation softens into a recommendation: "you should leave." The logic is identical to English "would": stepping a verb out of the indicative ("must") and into the conditional ("would have to" → "should") signals that you are offering advice, not issuing a command.
| Indicative (blunt) | Conditional (advice) | English |
|---|---|---|
| Trebuie să pleci. | Ar trebui să pleci. | You must / You should leave. |
| Trebuie să mănânci. | Ar trebui să mănânci ceva. | You must / You should eat something. |
| Trebuie să-l suni. | Ar trebui să-l suni. | You have to / You should call him. |
Crucially, ar trebui is invariable in exactly the way plain trebuie is. You do not conjugate it for person — there is no aș trebui for "I should," no am trebui for "we should." The form is ar trebui for everyone, and the person lives, as always, inside the să-clause that follows (see the subjunctive after modals).
Ar trebui să te odihnești, arăți epuizat.
You should rest, you look exhausted.
Cred că ar trebui să vorbim despre asta.
I think we should talk about this.
Ar trebui să-i mulțumești, te-a ajutat mult.
You ought to thank him, he helped you a lot.
Why this matters: tone
The gap between trebuie să and ar trebui să is the gap between giving an order and giving counsel. If a friend is tired, trebuie să te culci ("you have to go to bed") sounds bossy, almost parental; ar trebui să te culci ("you should go to bed") is gentle, the tone of a caring suggestion. Romanians feel this distinction sharply, and reaching for the indicative trebuie when you mean only to advise is the single most common way learners come across as brusque.
Nu vreau să te presez, dar ar trebui să te decizi curând.
I don't want to pressure you, but you should decide soon.
Ar trebui să citești cartea asta, ți-ar plăcea enorm.
You should read this book, you'd love it.
Other ways to say "should": the bine family
Ar trebui să is the workhorse, but Romanian has a small family of advice frames built on bine ("good / well"). They shade "should" toward "it would be a good idea to," and they all govern a să-clause.
| Form | Literal | Sense / register |
|---|---|---|
| ar fi bine să | it would be good to | "it'd be a good idea to" — soft, neutral |
| e bine să | it is good to | general good advice / rule of thumb |
| ai face bine să | you would do well to | firmer, edging toward a warning |
Ar fi bine să is the gentlest — it floats the idea as a hypothetical good. E bine să drops the conditional and states a general truth ("it's good to drink water"), the register of health tips and proverbs. Ai face bine să is the firm one: "you'd do well to," with a faint note of warning, the thing you say when the advice is really closer to a caution.
Ar fi bine să rezervi din timp, se umple repede.
It'd be a good idea to book in advance, it fills up fast.
E bine să bei multă apă pe căldura asta.
It's good to drink a lot of water in this heat.
Ai face bine să nu întârzii la interviu.
You'd do well not to be late for the interview. (firm, half-warning)
The past: "should have" = ar fi trebuit să
Here is where the system pays off. To say "should have" — advice or reproach about something that didn't happen — Romanian stacks the verb into the past conditional: ar fi + trebuit + să. Literally "it would have been-necessary that..." The pieces are: ar fi (the invariable past-conditional auxiliary) + trebuit (the past participle of a trebui) + the să-clause carrying the person.
Ar fi trebuit să-i spui adevărul de la început.
You should have told him the truth from the start.
Ar fi trebuit să plecăm mai devreme, acum prindem trafic.
We should have left earlier, now we'll hit traffic.
Îmi pare rău, ar fi trebuit să te ascult.
I'm sorry, I should have listened to you.
Again, ar fi trebuit is frozen — no person agreement on the modal block at all. Whether it's "I should have" or "they should have," the form stays ar fi trebuit să, and the să-verb does the work (să-i spui = you, să plecăm = we, să te ascult = I).
There is a competing form worth knowing. The imperfect trebuia să also covers "should have / was supposed to" (covered in detail on the a trebui page). The two overlap heavily, but there is a nuance: trebuia să-i spui frames it as a standing obligation that was left unfulfilled ("you were supposed to tell him"), while ar fi trebuit să-i spui frames it as a hypothetical, retrospective judgement ("the right thing would have been to tell him"). In everyday reproach they are near-interchangeable; ar fi trebuit leans a touch more reflective and counterfactual.
Trebuia să-l suni, dar ai uitat.
You were supposed to call him, but you forgot. (standing obligation, unfulfilled)
Ar fi trebuit să-l suni — ar fi apreciat.
You should have called him — he'd have appreciated it. (retrospective judgement)
Should not: negating advice
To advise against something, nu goes inside the să-clause, exactly as with any conjunctiv. Ar trebui să nu and n-ar trebui să both occur; the more idiomatic, lighter form pulls the negation onto the modal itself: n-ar trebui să ("shouldn't").
N-ar trebui să fumezi atât, îți face rău.
You shouldn't smoke so much, it's bad for you.
N-ar fi trebuit să spui asta în fața tuturor.
You shouldn't have said that in front of everyone.
Common Mistakes
❌ Trebuie să te odihnești. (intending gentle advice 'you should rest')
Too blunt for advice — trebuie is 'must'. For 'should', use the conditional ar trebui.
✅ Ar trebui să te odihnești.
You should rest.
❌ Aș trebui să plec acum.
Incorrect — ar trebui is invariable; there is no first-person aș trebui. The person lives in the să-clause.
✅ Ar trebui să plec acum.
I should leave now.
❌ Ar trebui să-i spuneai. (trying to say 'you should have told him')
Wrong structure for the past — don't put the second verb in the imperfect. Use the stacked past conditional ar fi trebuit să + present.
✅ Ar fi trebuit să-i spui.
You should have told him.
❌ Ar trebui plec mai devreme.
Incorrect — ar trebui requires să before the main verb, just like trebuie.
✅ Ar trebui să plec mai devreme.
I should leave earlier.
❌ Ar fi bine plecăm acum.
Incorrect — ar fi bine governs a să-clause: ar fi bine SĂ plecăm.
✅ Ar fi bine să plecăm acum.
It'd be a good idea to leave now.
Key Takeaways
- "Should / ought to" is the conditional of a trebui: ar trebui să — gentler advice against the blunt indicative trebuie să ("must").
- Ar trebui is invariable like trebuie — never aș trebui; the person sits in the să-clause.
- The bine family grades the advice: ar fi bine să (softest) → e bine să (general rule) → ai face bine să (firm, half-warning).
- "Should have" stacks into the past conditional: ar fi trebuit să-i spui ("you should have told him"), also frozen for person.
- Trebuia să (imperfect) overlaps with ar fi trebuit să for "should have"; the latter is the more counterfactual, reflective framing.
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Start learning Romanian→Related Topics
- a trebui (must / have to)A2 — The invariable modal trebuie for obligation and probability, the past a trebuit să, and the high-value imperfect trebuia să for 'should have / was supposed to'.
- Conjunctiv After Modals: a putea, a trebui, a vreaA2 — How modal and control verbs (a vrea, a putea, a trebui, a încerca, a reuși, a spera) force a să-clause where English uses an infinitive, and the one verb that still tolerates the infinitive.
- The Conditional for PolitenessA2 — The high-frequency polite formulas built on the conditional — aș vrea, aș dori, ați putea, mi-ar plăcea — that beginners need early for requests in restaurants, shops, and service situations.
- The Many Faces of trebuieB2 — trebuie is invariable and impersonal — never eu trebui — yet it wears many hats: trebuie să plec 'I must go' (the person lives in the să-clause), trebuie făcut 'it needs doing', evidential trebuie că doarme 'he must be asleep', and the dative îmi trebuie 'I need'. Plus the past forms trebuia să (was supposed to), ar trebui să (should), and a trebuit să (had to).
- Modal Verbs and Periphrases: ReferenceB1 — A consolidated lookup table mapping every English modal — can, must, should, may, need, want, might — to its Romanian expression and the clause it governs, with the forms, meanings, and the one rule that ties them all together: modal verb + să-clause.