Preterite of Ser and Ir | Portuguese (Portugal) Grammar

Here is the single strangest fact in Portuguese conjugation: the verbs ser (to be) and ir (to go) have completely identical forms in the preterite. Not similar -- identical. Every person, every number, the exact same word. This seems like it should cause endless confusion, but in practice it never does. Context always makes the meaning clear.

The conjugation

One table serves both verbs:

Person	Form	as ser (to be)	as ir (to go)
eu	fui	I was	I went
tu	foste	you were	you went
ele / ela / você	foi	he/she was; you were	he/she went; you went
nós	fomos	we were	we went
(vós)	(fostes)	(you all were)	(you all went)
eles / elas / vocês	foram	they were; you all were	they went; you all went

Fui professor durante dez anos.

I was a teacher for ten years.

Fui ao cinema ontem à noite.

I went to the cinema last night.

Both sentences use fui, but the first one means "I was" and the second means "I went." The surrounding words remove all doubt.

How to tell them apart

Three patterns make disambiguation automatic:

Followed by a/para + place = ir. Movement toward a destination signals "to go."

Followed by a noun or adjective describing identity, quality, or an event = ser. If the sentence describes what something was or what someone was, it is ser.

Followed by an infinitive = ir. This is the periphrastic past, expressing "went to do something."

Sentence	Verb	Translation	Clue
Fui a Lisboa.	ir	I went to Lisbon.	a + place
Fui professor.	ser	I was a teacher.	noun (identity)
Foi difícil.	ser	It was difficult.	adjective (quality)
Foi ao banco.	ir	He went to the bank.	a + place
Fomos felizes.	ser	We were happy.	adjective (state)
Fomos à praia.	ir	We went to the beach.	a + place
Foram buscar o carro.	ir	They went to get the car.	infinitive
Foram os melhores alunos.	ser	They were the best students.	noun (identity)

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When you see a form of fui/foi/foram followed by a, ao, à, para, or an infinitive, it is almost always ir. When followed by a noun, adjective, or nothing at all (in short answers), it is almost always ser. Native speakers never hesitate -- the context does all the work.

Ser in the preterite -- uses

Use the preterite of ser to describe what something was -- completed judgements, identities, and events in the past.

Foi bom.

It was good.

O concerto foi fantástico.

The concert was fantastic.

Ele foi médico durante trinta anos.

He was a doctor for thirty years.

A reunião foi às três.

The meeting was at three.

Notice that the preterite of ser often appears with adjectives (bom, fantástico, difícil), professions (médico, professor), and time expressions for events (às três, em 2020). Whenever you are describing a finished evaluation or a past identity, you are using ser.

Ir in the preterite -- uses

Use the preterite of ir to describe where someone went -- completed movement to a destination or purpose.

Fui ao supermercado.

I went to the supermarket.

Fomos à praia no domingo.

We went to the beach on Sunday.

Foram para casa cedo.

They went home early.

Fui buscar as crianças à escola.

I went to pick up the kids from school.

The prepositions a (to, for a short visit) and para (to, for a longer stay or direction) are the clearest markers. When ir is followed directly by an infinitive (fui buscar, foi comprar), it expresses purpose -- "went to do something."

Why are they identical?

This is not a quirk of Portuguese alone. In Vulgar Latin, the verbs esse (to be) and ire (to go) gradually merged their past-tense forms. The same convergence happened in Spanish (fui, fue, fueron serve both ser and ir), Catalan, and other Romance languages. By the time the modern languages emerged, speakers had been disambiguating by context for centuries. The system works because the meanings of "to be" and "to go" are so different that the surrounding sentence always makes the intended verb obvious.

Fomos vs fôramos -- don't confuse the tenses

The preterite fomos (we went / we were) should not be confused with the pluperfect fôramos (we had gone / we had been). The pluperfect is a literary form that appears in written texts and formal speech but is rarely used in everyday conversation. In spoken EP, the compound pluperfect (tínhamos ido / tínhamos sido) replaces it.

Tense	Form	Meaning	Usage
Preterite	fomos	we went / we were	everyday speech and writing
Pluperfect	fôramos	we had gone / we had been	literary and formal texts

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At the A2 level, you only need the preterite forms. If you encounter fora, foras, fôramos, or foram with a circumflex in a text, recognise them as the literary pluperfect -- but do not worry about producing them yourself yet.

For the full picture of the preterite tense, see Preterite Overview. For the present-tense forms of these verbs, see Present Indicative: Ser and Present Indicative: Ir and Vir. For the difference between ser and estar, see Ser, Estar, and Ficar.