Dever (To Owe/Must) — Full Conjugation

Dever is one of the most useful verbs in Portuguese precisely because it wears so many hats. In its most transparent sense, it means to owe — money, a favour, an apology. But its real power is as a modal verb: deves estudar (you should/must study) expresses obligation; ele deve estar em casa (he's probably home) expresses likelihood. These two modal readings — obligation and probability — sit side by side in the same tense forms, and context alone tells you which is meant. A third, more traditional construction, dever de + infinitive, was once reserved for probability only, keeping dever + infinitive for obligation; that distinction is still taught by prescriptive grammars but is largely collapsed in modern speech.

This page gives you every conjugated form of dever, organized tense by tense, plus a detailed guide to its four core uses.

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Present indicative — presente do indicativo

Use this tense for current obligations, habits, general truths, and present probability. Devo cinco euros ao João = I owe João five euros. Deves descansar = You should rest.

Imperfect indicative — pretérito imperfeito

Use this tense for past habits, background states of obligation, and the very common softening use: devias ir ao médico (you should go to the doctor) — present advice, past-tense form.

Preterite indicative — pretérito perfeito simples

Use this tense for completed past actions of owing or having been obligated.

Pluperfect indicative, simple — pretérito mais-que-perfeito simples

A literary synthetic form. In everyday speech, use the compound pluperfect below.

Pluperfect indicative, compound — pretérito mais-que-perfeito composto

The everyday way to say had owed or should have. Formed with the imperfect of ter plus devido.

Present perfect — pretérito perfeito composto

Describes a repeated or continuous state of owing or being obligated up to now. Tenho devido muito a esta equipa = I've owed a lot to this team (recently / lately).

Simple future — futuro do indicativo simples

Used for future obligations and future probabilities. In speech, ir + infinitive (vou dever) is more common.

Future perfect — futuro perfeito

Conditional — condicional (futuro do pretérito)

The classic "should / ought to" construction. Deveria telefonar-lhe = I should call him.

Conditional perfect — condicional composto

Describes would have owed or, more commonly, should have [done something]. Deveria ter ligado = I should have called.

Present subjunctive — presente do conjuntivo

Imperfect subjunctive — imperfeito do conjuntivo

Future subjunctive — futuro do conjuntivo

Present perfect subjunctive — pretérito perfeito do conjuntivo

Pluperfect subjunctive — pretérito mais-que-perfeito do conjuntivo

Future perfect subjunctive — futuro perfeito do conjuntivo

Imperative — imperativo

The imperative of dever exists morphologically but is rarely used — you do not usually command someone to "owe" something. The forms follow the regular pattern.

Affirmative:

Negative (identical to the present subjunctive with não):

Personal infinitive — infinitivo pessoal

The four uses of dever

1. Dever + noun = to owe

The literal, transitive use. The thing owed is the direct object; the person owed takes the preposition a.

2. Dever + infinitive = must / should (obligation)

Expresses obligation, duty, or strong recommendation. This is the most common modal use.

3. Dever + infinitive = probably (epistemic)

The same form also expresses likelihood or inference — "must be" in the English sense of probability, not obligation. Context disambiguates.

4. Dever de + infinitive = probably (traditional)

Historically, prescriptive grammars reserved dever + infinitive for obligation and dever de + infinitive for probability. Ele deve de estar com fome = he must be hungry (probability).

In modern spoken European Portuguese, this distinction has largely collapsed: most speakers use dever + infinitive for both obligation and probability, letting context sort them out. You will still meet dever de + infinitive in careful writing, older literature, and the speech of more conservative speakers. It is never wrong to use it for probability; many educated Portuguese consider it the more elegant choice.

Example sentences in context

Common mistakes

Key takeaways

• Dever is a regular second-conjugation (-er) verb. Every form is predictable.
• Four core uses: owe (dever + noun), must/should (dever + infinitive, obligation), probably (dever + infinitive, epistemic), and the traditional dever de + infinitive for probability.
• Prescriptive grammar distinguishes dever (obligation) from dever de (probability). Modern speech mostly uses plain dever for both, but dever de is still respected in writing.
• Dever for obligation is weaker than ter de. For strong necessity, prefer ter de; for recommendation, use dever.
• In European Portuguese, the imperfect devia(s) often replaces the conditional deveria(s) for softened advice in everyday speech.