Debeo: To Owe or Ought | Latin Grammar

Dēbeō joins two ideas that English normally separates: owing something and being under an obligation to act. Its principal parts are dēbeō, dēbēre, dēbuī, dēbitum. With a noun it usually means “owe”; with a complementary infinitive it means “ought, should, be obliged to.”

All unlabelled uses below are normal Classical prose. Dēbeō describes an obligation as something due from a person, which explains its connection with debt: historically and synchronically, what one “ought” to do is conceived as something owed.

Stems and a Form-First Diagnostic

The present stem dēbē- produces dēbeō, dēbēbam, and dēbēbō. The perfect active stem dēbu- produces dēbuī and dēbueram. The supine stem dēbit- produces the perfect passive participle dēbitus and future participle dēbitūrus. Do not invent dēbēvī from the infinitive: the third principal part supplies the actual stem.

When reading, first find the stem and ending. Next ask whether dēbeō has a noun object (“owe X”) or an infinitive (“ought to do X”). Only then choose the English wording.

Quīnque dēnāriōs tibi dēbeō.

I owe you five denarii.

Ante noctem domum redīre dēbēmus.

We ought to return home before nightfall.

Complete Active Indicative

Tense	1st sg.	2nd sg.	3rd sg.	1st pl.	2nd pl.	3rd pl.
Present	dēbeō	dēbēs	dēbet	dēbēmus	dēbētis	dēbent
Imperfect	dēbēbam	dēbēbās	dēbēbat	dēbēbāmus	dēbēbātis	dēbēbant
Future	dēbēbō	dēbēbis	dēbēbit	dēbēbimus	dēbēbitis	dēbēbunt
Perfect	dēbuī	dēbuistī	dēbuit	dēbuimus	dēbuistis	dēbuērunt / dēbuēre
Pluperfect	dēbueram	dēbuerās	dēbuerat	dēbuerāmus	dēbuerātis	dēbuerant
Future perfect	dēbuerō	dēbueris	dēbuerit	dēbuerimus	dēbueritis	dēbuerint

Herī ad iūdicem venīre dēbēbās.

You were supposed to come before the judge yesterday.

Crās pecūniam solvere dēbēbit.

Tomorrow he will have to pay the money.

With an infinitive, perfect dēbuī often implies an unfulfilled duty: venīre dēbuī can mean “I ought to have come.” Context can instead make it a simple past obligation, “I had to come.” Latin does not mechanically encode the English distinction between “had to” and “should have.”

Tē statim certiōrem facere dēbuī.

I ought to have informed you at once.

Complete Active Subjunctive

Tense	1st sg.	2nd sg.	3rd sg.	1st pl.	2nd pl.	3rd pl.
Present	dēbeam	dēbeās	dēbeat	dēbeāmus	dēbeātis	dēbeant
Imperfect	dēbērem	dēbērēs	dēbēret	dēbērēmus	dēbērētis	dēbērent
Perfect	dēbuerim	dēbuerīs	dēbuerit	dēbuerīmus	dēbuerītis	dēbuerint
Pluperfect	dēbuissem	dēbuissēs	dēbuisset	dēbuissēmus	dēbuissētis	dēbuissent

Nesciō quantum mercātōrī dēbeam.

I do not know how much I owe the merchant.

Sī officium facere dēbērēs, nōn recūsārēs.

If you were obliged to perform the duty, you would not refuse.

The visible form dēbuerit can be future perfect indicative or perfect subjunctive. A future condition points to the former; an indirect question or subordinate clause requiring subjunctive points to the latter.

Passive: What Is Owed Becomes the Subject

In the debt sense, dēbeō is transitive and has a genuine personal passive. Active decem aureōs tibi dēbeō corresponds structurally to decem aureī tibi dēbentur: “ten gold pieces are owed to you.” The creditor remains dative.

Tense/mood	1st sg.	2nd sg.	3rd sg.	1st pl.	2nd pl.	3rd pl.
Present indicative	dēbeor	dēbēris	dēbētur	dēbēmur	dēbēminī	dēbentur
Imperfect indicative	dēbēbar	dēbēbāris	dēbēbātur	dēbēbāmur	dēbēbāminī	dēbēbantur
Future indicative	dēbēbor	dēbēberis	dēbēbitur	dēbēbimur	dēbēbiminī	dēbēbuntur
Perfect indicative	dēbitus sum	dēbitus es	dēbitus est	dēbitī sumus	dēbitī estis	dēbitī sunt
Pluperfect indicative	dēbitus eram	dēbitus erās	dēbitus erat	dēbitī erāmus	dēbitī erātis	dēbitī erant
Future perfect indicative	dēbitus erō	dēbitus eris	dēbitus erit	dēbitī erimus	dēbitī eritis	dēbitī erunt
Present subjunctive	dēbear	dēbeāris	dēbeātur	dēbeāmur	dēbeāminī	dēbeantur
Imperfect subjunctive	dēbērer	dēbērēris	dēbērētur	dēbērēmur	dēbērēminī	dēbērentur
Perfect subjunctive	dēbitus sim	dēbitus sīs	dēbitus sit	dēbitī sīmus	dēbitī sītis	dēbitī sint
Pluperfect subjunctive	dēbitus essem	dēbitus essēs	dēbitus esset	dēbitī essēmus	dēbitī essētis	dēbitī essent

The table gives masculine subjects in the perfect system. Change dēbitus, dēbitī to agree with the actual subject: feminine merces dēbita est, neuter plural praemia dēbita sunt. These forms are most natural of a concrete debt or something properly due; they are less usual as personal paraphrases of modal “ought.”

Mercēs operāriīs nōndum dēbēbātur.

The pay was not yet owed to the workers.

Praemium victōrī dēbitum est.

A reward was owed to the victor.

Commands and Non-Finite Forms

Present imperatives are dēbē, dēbēte, though commanding someone to “owe” is pragmatically uncommon. Future dēbētō, dēbētōte, dēbentō is (formal/archaic). Passive imperatives dēbēre, dēbēminī are morphologically regular but rare because debts are not usually commanded into existence.

Category	Active	Passive
Present infinitive	dēbēre	dēbērī
Perfect infinitive	dēbuisse	dēbitum esse
Future infinitive	dēbitūrum esse	dēbitum īrī, rare
Participles	dēbēns; dēbitūrus	dēbitus; dēbendus
Gerund	dēbendī, dēbendō, dēbendum, dēbendō	—
Supines	dēbitum, dēbitū	—

Cōnstat eum pecūniam dēbuisse.

It is agreed that he owed the money.

Sciēbat sē poenās datūrum esse, nisi tantum dēbitum solveret.

He knew that he would pay the penalty unless he settled so great a debt.

The adjective-like participle dēbitus commonly means “due, proper, deserved”: honor dēbitus “the honor due.” It may describe obligation without asserting an event of “being owed.” The gerundive dēbendus is possible but much less common; Classical prose normally uses dēbitus or active dēbeō.

Nouns, Infinitives, and Word Order

In the debt construction, the amount or thing owed is accusative and the creditor is dative: pecūniam frātrī dēbet. In the passive, the thing owed becomes nominative while the creditor remains dative: pecūnia frātrī dēbētur.

With an infinitive, the subject of dēbeō is normally also the understood subject of the infinitive: mīlitēs proficīscī dēbent “the soldiers ought to depart.” If the required action itself is passive, keep dēbeō active and make the dependent infinitive passive.

Pons ante hiemem reficī dēbet.

The bridge ought to be repaired before winter.

This is dēbet plus passive reficī, not passive dēbētur. The bridge is the subject of “ought” and the patient of “be repaired.” English “is supposed to be repaired” can tempt learners toward the wrong voice on dēbeō.

For Latin's distinct construction with a gerundive and dative of agent, see Passive Periphrastic and Obligation.

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Parse the two verbs separately: in porta claudī dēbet, dēbet is third-person singular active, while claudī is present passive infinitive. The sentence has modal force because of dēbeō, not because dēbeō is passive.

Classical Latin has no major productive set of everyday compounds of dēbeō comparable to those of ferō or eō. Later or rare prefixed formations should be learned from their own evidence, not generated by rule. The important word family instead includes dēbitum “a debt” and indēbitus “not owed, undeserved.”

Common Mistakes

Inventing a regular perfect

❌ Pecūniam dēbēvī.

Incorrect — the perfect stem is dēbu-, not dēbēv-.

✅ Pecūniam dēbuī.

I owed the money.

Using an accusative for the creditor

❌ Decem dēnāriōs amīcum dēbeō.

Incorrect — the person to whom the debt is due is dative.

✅ Decem dēnāriōs amīcō dēbeō.

I owe my friend ten denarii.

Making dēbeō passive instead of the infinitive

❌ Pons reficere dēbētur.

Incorrect for ‘the bridge ought to be repaired.’

✅ Pons reficī dēbet.

The bridge ought to be repaired.

Assuming past obligation was fulfilled

❌ Venīre dēbuī, ergō vēnī.

Faulty inference — dēbuī can introduce an unfulfilled duty.

✅ Venīre dēbuī, sed domī mānsī.

I ought to have come, but I stayed at home.

Key Takeaways

Learn dēbeō, dēbēre, dēbuī, dēbitum as a four-part unit.
A noun complement gives the debt sense; an infinitive gives obligation.
The thing owed is accusative in the active and nominative in the passive; the creditor is dative in both.
In reficī dēbet, the infinitive—not dēbeō—is passive.

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