Supporre (to suppose, to assume) is built from the prefix sup- ("under", an assimilated form of sub-) plus porre, giving etymologically "to put under" — that is, to lay something down as an underlying assumption. The Latin source is suppōnere, and the metaphor — placing a hypothesis underneath your reasoning — is preserved in English suppose, French supposer, Spanish suponer. As with all porre derivatives, the conjugation follows the parent verb's irregular paradigm form-for-form, with sup- glued onto every cell.
What makes supporre especially worth learning at B1 is its grammatical role: it is a classic subjunctive trigger. Like credere, pensare, immaginare, sperare, dubitare, it expresses subjective belief or speculation rather than asserted fact, so the subordinate clause introduced by che takes the congiuntivo.
Indicativo presente
| Person | Form |
|---|---|
| io | suppongo |
| tu | supponi |
| lui / lei / Lei | suppone |
| noi | supponiamo |
| voi | supponete |
| loro | suppongono |
The same g-stem alternation as porre: suppong- in 1sg and 3pl, plain suppon- elsewhere. The doubled -pp- in the prefix comes from Latin sub assimilating to the following p of ponere — the same process that gave us opporre (op- ← ob-) and imporre (im- ← in-).
Suppongo che sia in ritardo per il traffico.
I suppose he's late because of traffic.
Supponi che lei abbia ragione: cosa faresti?
Suppose she's right — what would you do?
Il regolamento suppone che ogni partecipante abbia letto le istruzioni.
The rules assume that every participant has read the instructions.
Supponiamo per un momento che tu non sia d'accordo.
Let's suppose for a moment that you don't agree.
Tutti suppongono che la decisione sia già stata presa.
Everyone is assuming the decision has already been made.
The subjunctive trigger
Because supporre expresses speculation rather than fact, che + congiuntivo is the standard pattern. This is non-negotiable in good Italian — using the indicative after suppongo che sounds wrong to a native speaker.
Suppongo che tu abbia già visto il film.
I suppose you've already seen the film.
Suppongo che siano arrivati in tempo.
I assume they got there on time.
Lei suppone che noi non sappiamo niente.
She assumes we don't know anything.
When the speculation is about a present-time fact, use congiuntivo presente. When it's about a past fact, use congiuntivo passato (che + abbia/sia + participle). After past tenses of supporre itself, the imperfetto subjunctive comes in (supponevo che fosse vero).
Imperfetto
| Person | Form |
|---|---|
| io | supponevo |
| tu | supponevi |
| lui / lei / Lei | supponeva |
| noi | supponevamo |
| voi | supponevate |
| loro | supponevano |
Supponevo che sapessi già la notizia.
I assumed you already knew the news.
Passato remoto
| Person | Form |
|---|---|
| io | supposi |
| tu | supponesti |
| lui / lei / Lei | suppose |
| noi | supponemmo |
| voi | supponeste |
| loro | supposero |
The 1-3-3 strong stem suppos- parallels porre → posi/pose/posero. Form: supposi, NOT supponsi.
Inizialmente supposi che fosse uno scherzo.
At first I assumed it was a joke.
Futuro semplice
| Person | Form |
|---|---|
| io | supporrò |
| tu | supporrai |
| lui / lei / Lei | supporrà |
| noi | supporremo |
| voi | supporrete |
| loro | supporranno |
Doubled-rr from n→r assimilation. Note that the future is rare in everyday use — speakers far more often reach for the present (suppongo che...) for general assumptions.
A quel punto supporranno che siamo già partiti.
At that point they'll assume we've already left.
Condizionale presente
| Person | Form |
|---|---|
| io | supporrei |
| tu | supporresti |
| lui / lei / Lei | supporrebbe |
| noi | supporremmo |
| voi | supporreste |
| loro | supporrebbero |
Supporrei di sì, ma è meglio chiedere.
I'd assume so, but it's better to ask.
Congiuntivo presente
| Person | Form |
|---|---|
| (che) io | supponga |
| (che) tu | supponga |
| (che) lui / lei | supponga |
| (che) noi | supponiamo |
| (che) voi | supponiate |
| (che) loro | suppongano |
You'll most often need the subjunctive of supporre itself when it appears in a higher-order subordinate clause: credo che lui supponga... / non penso che lei supponga...
Non credo che lui supponga niente di strano.
I don't think he's assuming anything strange.
Congiuntivo imperfetto
| Person | Form |
|---|---|
| (che) io | supponessi |
| (che) tu | supponessi |
| (che) lui / lei | supponesse |
| (che) noi | supponessimo |
| (che) voi | supponeste |
| (che) loro | supponessero |
Se supponessi davvero che fosse colpa mia, te lo direi.
If I really thought it were my fault, I'd tell you.
Imperativo
| Person | Form |
|---|---|
| tu | supponi |
| Lei (formal) | supponga |
| noi | supponiamo |
| voi | supponete |
| loro (formal pl.) | suppongano |
The most-used imperative form is the noi form supponiamo — used as a thought-experiment opener equivalent to English "Suppose..." or "Let's say...". This is one of the genuinely useful imperative forms in Italian discourse.
Supponiamo che tu vinca alla lotteria: cosa faresti per primo?
Suppose you win the lottery — what would you do first?
Supponi un attimo di essere al posto suo.
Just suppose for a moment you were in her shoes.
Forme non finite
| Form | Italian |
|---|---|
| Infinito presente | supporre |
| Infinito passato | aver supposto |
| Gerundio presente | supponendo |
| Gerundio passato | avendo supposto |
| Participio passato | supposto |
The participle supposto is also used as an adjective meaning "supposed, alleged" — il supposto colpevole (the alleged culprit), la supposta verità (the supposed truth). The feminine singular supposta has, by an etymological coincidence, also come to mean "suppository" (a medical qualcosa che si pone sotto) — context resolves which sense is intended.
Compound tenses
Auxiliary: avere. Participle: supposto.
| Tense | io | noi |
|---|---|---|
| Passato prossimo | ho supposto | abbiamo supposto |
| Trapassato prossimo | avevo supposto | avevamo supposto |
| Futuro anteriore | avrò supposto | avremo supposto |
| Condizionale passato | avrei supposto | avremmo supposto |
| Congiuntivo passato | abbia supposto | abbiamo supposto |
| Congiuntivo trapassato | avessi supposto | avessimo supposto |
Avevo supposto che fosse tutto a posto, ma mi sbagliavo.
I had assumed everything was fine, but I was wrong.
Distinctive uses and constructions
| Italian | English |
|---|---|
| supporre che + congiuntivo | to suppose that... (the canonical pattern) |
| supporre di + infinitive | to suppose oneself to (when subjects coincide) |
| è da supporre che | it can be assumed that... |
| il supposto colpevole | the alleged culprit |
| una supposta verità | a supposed truth |
| posto / supposto che | granted that, assuming that (formal) |
È da supporre che la situazione si risolva in tempi brevi.
It can be assumed that the situation will resolve itself quickly.
Suppongo di sì, ma non ne sono certa.
I suppose so, but I'm not sure.
Posto che tu abbia ragione, cosa cambia per me?
Granted that you're right, what changes for me?
Il presunto colpevole è stato rilasciato per insufficienza di prove.
The alleged culprit was released for lack of evidence. (presunto is the more common synonym in legal contexts)
Common mistakes
❌ Suppongo che lui ha ragione.
Incorrect — supporre triggers the subjunctive.
✅ Suppongo che lui abbia ragione.
Correct — abbia is the congiuntivo presente.
❌ Supponerò che sia tutto a posto.
Incorrect — the future stem is contracted to supporr-.
✅ Supporrò che sia tutto a posto.
Correct — supporrò, with double-r.
❌ Ho supponuto che fosse a casa.
Incorrect — supponuto is a non-form.
✅ Ho supposto che fosse a casa.
Correct — the participle is supposto.
❌ Suppongo lui sia stanco.
Incorrect in standard register — Italian normally requires che before the subjunctive clause.
✅ Suppongo che lui sia stanco.
Correct — keep the che.
❌ Supponsi un momento di essere in vacanza.
Incorrect — the imperative tu form is supponi, not supponsi. There is no -s in Italian verb endings.
✅ Supponi un momento di essere in vacanza.
Correct — supponi, identical to the indicative tu form.
Key takeaways
Supporre conjugates identically to porre, with the prefix sup- (assimilated sub-) prepended to every form. The participle is supposto (parallel to posto).
Three points to internalise:
Suppongo / supponga — the g-stem 1sg and the entire congiuntivo presente.
Supporre triggers the subjunctive in che-clauses, exactly like credere, pensare, immaginare, sperare, dubitare. Suppongo che sia, suppongo che abbia, suppongo che siano — drill these and the broader subjunctive-after-thought-verbs pattern locks in.
Supponiamo is the discourse-marker noi-form, equivalent to English "Suppose..." / "Let's say...". Genuinely useful for hypothetical conversations.
Now practice Italian
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Open the Italian course →Related Topics
- Porre: Full ConjugationB1 — Complete paradigm of porre (to place, to pose) — a hidden-stem verb whose two-syllable infinitive masks the Latin pon- stem that surfaces throughout the conjugation, and the model paradigm for an entire family of common derivatives.
- Proporre: Full ConjugationB1 — Complete paradigm of proporre (to propose, to suggest) — a porre-family derivative that conjugates identically to its parent verb but, unlike formal porre, is entirely natural in everyday conversation.
- Comporre: Full ConjugationB1 — Complete paradigm of comporre (to compose, to dial) — a porre-family derivative covering everything from musical composition to dialing a phone number.
- Presente: Porre and Its Derivatives (proporre, comporre, opporre, supporre, esporre)B1 — Why this two-syllable infinitive hides a Latin -ponere stem — and how mastering one verb unlocks ten more (proporre, comporre, opporre, supporre, esporre, imporre, disporre, sottoporre, anteporre, posporre).