Saber (To Know) — Full Conjugation

Saber means to know — but only in the sense of knowing a fact, a piece of information, or how to do something. If you want to say you know a person, a place, or a work of art (meaning you are familiar with it), you reach for conhecer instead. Portuguese draws a line English does not: sei matemática (I know maths — the facts of it), but conheço o professor de matemática (I know the maths teacher — I am acquainted with him). This is the single most important thing to learn about saber, and the rest of this page assumes you understand it.

Saber is one of the most irregular verbs in Portuguese. The eu form of the present is sei (not sabo), the entire present subjunctive is built on an unpredictable stem saib-, and the preterite is a so-called strong preterite with shifted stress and its own special meaning: soube does not mean I knew, it means I found out. You have to memorize every tense; there is no pattern that gets you there.

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Present indicative — presente do indicativo

The eu form is sei. This is an ancient irregularity inherited from Latin sapio and shared with Spanish sé. Every other form is built on the regular stem sab-.

Imperfect indicative — pretérito imperfeito

Regular, built on sab-. This is the tense you use for I knew, I used to know (an ongoing state of knowledge in the past).

Preterite indicative — pretérito perfeito simples

A strong (rizotonic) preterite: the stress falls on the stem soub-, not the ending. And crucially, the preterite has a shifted meaning: soube means I found out, I came to know, I learned — the moment knowledge entered your head. To say I knew, use the imperfect.

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

Literary; everyday speech uses the compound. Built on the preterite stem soub-.

The eles form souberam is identical to the preterite; context disambiguates.

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

Present perfect — pretérito perfeito composto

Repeated or continuous action up to now. Tenho sabido de muita coisa sobre ele — I've been finding out a lot about him (lately).

Simple future — futuro do indicativo simples

Regular on the stem saber-.

Future perfect — futuro perfeito

Conditional — condicional (futuro do pretérito)

Conditional perfect — condicional composto

Present subjunctive — presente do conjuntivo

Built on the unpredictable stem saib-. This is not derived from the eu form (sei) by the usual rule — saber is one of six classic irregulars (along with ser, estar, ir, dar, querer, haver) whose present subjunctive you simply have to memorize.

Imperfect subjunctive — imperfeito do conjuntivo

Built on the preterite stem soub-.

Future subjunctive — futuro do conjuntivo

Also built on soub-. Used after se, quando, enquanto, and other future-looking conjunctions.

Notice: the future subjunctive souber is different from the personal infinitive saber. Unlike regular verbs, these two tenses are not identical for saber.

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 tu affirmative is the regular sabe; everything else uses the subjunctive stem saib-. Affirmative commands with saber are rare in everyday life — know this! is an awkward thing to order — but saiba que... is a polite formal opener meaning let me tell you that... / be aware that....

Affirmative:

Negative (subjunctive with não):

Personal infinitive — infinitivo pessoal

Regular, built on the infinitive saber.

Compound personal infinitive — infinitivo pessoal composto

Usage notes

Saber vs. conhecer — the central distinction

English uses to know for everything. Portuguese splits it in two:

• Saber = to know a fact, a piece of information, or how to do something. Something that can be stated, written down, or demonstrated.
• Conhecer = to be acquainted with a person, a place, a book, a work of art, a field of study. Familiarity through experience.

So sei a resposta (I know the answer), but conheço a cidade (I know the city). Sei quem ele é (I know who he is — the fact of his identity), but conheço-o há anos (I've known him for years — I am acquainted with him).

Saber + infinitive = to know how to

With an infinitive, saber means to know how to. Portuguese does not insert como (how) — the infinitive alone does the work.

Não sei se — embedded questions

Não sei se + indicative introduces an embedded yes/no question. This takes the indicative, not the subjunctive — because it is an information question, not an expression of doubt about the truth of the proposition.

Preterite special meaning: soube = found out

This is worth repeating: soube does not mean I knew. It means I found out, I came to know, I learned. The Portuguese preterite of verbs of mental state often shifts meaning this way (compare conheci = I met (for the first time), not I knew). If you want to say I already knew, use the imperfect sabia — often with já: já sabia.

Saber a + noun = to taste of

There is a separate, common use of saber meaning to taste (of): este café sabe a queimado = this coffee tastes burnt. This is not knowledge at all — it is a different lexical meaning that happens to share the same verb.

Example sentences in context

Common mistakes

Key takeaways

• Saber = know a fact, information, or how to do something. Conhecer = be acquainted with a person, place, or work. These are not interchangeable.
• The eu-present is sei (irregular). The rest of the present uses the regular stem sab-.
• The preterite is strong and stress-shifted: soube, soubeste, soube, soubemos, souberam — and the meaning shifts too. Soube = found out, not knew. For knew (state), use the imperfect sabia.
• The present subjunctive is built on the unpredictable stem saib-: saiba, saibas, saiba, saibamos, saibam.
• The imperfect and future subjunctive are built on soub-: soubesse... and souber....
• Saber
  • infinitive means to know how to — no como is needed.
• The second meaning of saber is to taste (of), used with a: sabe a limão = it tastes of lemon. This is not a mistake to avoid; it is a legitimate, common use.