Savoir is the verb you use when you know a fact, when you know how to do something, or when you know that a piece of information is true. It is one of the two French verbs that translate English know — the other being connaître, which means to be acquainted with (people, places, works of art). The split between them is one of the first hard distinctions an English speaker has to internalize when learning French.
This page is the full reference: every paradigm, the conjugational quirks (the sau- futur stem, the sache- subjunctive stem, the unusual gerundive sachant), the major uses, the aspectual shift in the passé composé, and the high-frequency idioms. For the savoir/connaître contrast specifically, see choosing/savoir-vs-connaitre.
The simple tenses
Présent de l'indicatif
The present has two stems: sai- in the singular (all three forms pronounced /sɛ/, homophonous with ses, ces, and c'est) and sav- in the plural. Highly irregular.
| Person | Form | Pronunciation |
|---|---|---|
| je | sais | /sɛ/ |
| tu | sais | /sɛ/ |
| il / elle / on | sait | /sɛ/ |
| nous | savons | /savɔ̃/ |
| vous | savez | /save/ |
| ils / elles | savent | /sav/ |
The most frequent form by far is je sais — and its negation je ne sais pas (often pronounced jsais pas /ʃɛpa/) is the single most common reply in French conversation when someone asks something you don't know.
Je sais qu'il est au bureau, mais je ne sais pas à quelle heure il rentre.
I know he's at the office, but I don't know what time he'll be back.
Tu sais conduire ? — Oui, j'ai mon permis depuis dix ans.
Do you know how to drive? — Yes, I've had my license for ten years.
Imparfait
Built on the plural stem sav- plus the regular imparfait endings.
| Person | Form |
|---|---|
| je | savais |
| tu | savais |
| il / elle / on | savait |
| nous | savions |
| vous | saviez |
| ils / elles | savaient |
The imparfait je savais corresponds to English I knew in its stative sense. Je savais qu'il viendrait = "I knew he'd come" (state of knowledge that existed in the past). This contrasts crucially with j'ai su, which means "I found out" — see the passé composé section below.
Je savais qu'on aurait des problèmes, je l'avais dit dès le début.
I knew we'd have problems, I'd said so from the start.
On ne savait pas que tu étais arrivé, sinon on serait venu te chercher.
We didn't know you'd arrived, otherwise we would have come to pick you up.
Passé simple (literary)
Stem su- with -us- class endings. Restricted to literary writing.
| Person | Form |
|---|---|
| je | sus |
| tu | sus |
| il / elle / on | sut |
| nous | sûmes |
| vous | sûtes |
| ils / elles | surent |
The circumflex on sûmes and sûtes is mandatory.
Il sut alors que sa vie allait changer.
He then knew his life was about to change. (literary)
Futur simple
Stem sau- — irregular and unrelated to the infinitive. Endings are the regular futur endings.
| Person | Form |
|---|---|
| je | saurai |
| tu | sauras |
| il / elle / on | saura |
| nous | saurons |
| vous | saurez |
| ils / elles | sauront |
Je te dirai dès que je saurai à quelle heure j'arrive.
I'll let you know as soon as I know what time I'm arriving.
On saura le résultat des élections demain matin.
We'll know the election results tomorrow morning.
Conditionnel présent
Same stem sau- as the futur, with the imparfait endings.
| Person | Form |
|---|---|
| je | saurais |
| tu | saurais |
| il / elle / on | saurait |
| nous | saurions |
| vous | sauriez |
| ils / elles | sauraient |
The conditionnel of savoir has a distinctive idiomatic use: je ne saurais + infinitive = I couldn't possibly / I wouldn't know how to (formal, slightly literary).
Je ne saurais vous dire à quel point je suis ému.
I can't begin to tell you how moved I am. (formal)
Tu saurais répondre à cette question ?
Would you know how to answer that question?
Subjonctif présent
Highly irregular. The stem is sach-, a form that appears nowhere else in the indicative paradigm.
| Person | Form |
|---|---|
| (que) je | sache |
| (que) tu | saches |
| (qu')il / elle / on | sache |
| (que) nous | sachions |
| (que) vous | sachiez |
| (qu')ils / elles | sachent |
The fixed expression que je sache (= "as far as I know") is one of the few places the subjunctive appears in casual speech without an explicit trigger.
Il n'a pas appelé, que je sache.
He hasn't called, as far as I know.
Il faut que tu saches la vérité.
You need to know the truth.
Impératif
Built on the subjunctive stem sach-, not on the indicative.
| Person | Form |
|---|---|
| (tu) | sache |
| (nous) | sachons |
| (vous) | sachez |
The imperative of savoir is unusual because it functions less like a command ("know!") and more like a discourse marker meaning let me tell you / be aware.
Sachez que je n'accepterai jamais ce contrat.
Let it be known that I'll never accept this contract. (formal)
Sache que je suis là si tu as besoin.
Know that I'm here if you need me.
Participles
- Participe passé: su (feminine sue, plural sus / sues)
- Participe présent: sachant (irregular, built on the subjunctive stem)
- Gérondif: en sachant
The present participle sachant is the source of the very common locution non-sachant (the non-experts) and the formal participial phrase sachant que ("knowing that").
En sachant ce que tu sais maintenant, tu aurais agi autrement ?
Knowing what you know now, would you have acted differently?
The compound tenses
Savoir uses avoir as its auxiliary.
Passé composé — the aspectual shift
avoir (présent) + su
The passé composé of savoir does not mean "I knew" — it means "I found out" or "I learned (a fact)". This is one of the most counter-intuitive aspectual shifts in French for English speakers, who naturally translate I knew as j'ai su. Don't.
| French | English |
|---|---|
| je savais | I knew (I was in a state of knowing) |
| j'ai su | I found out / I learned (a transition into knowing) |
The same shift happens with connaître: je connaissais = "I knew (a person)"; j'ai connu = "I met (for the first time)" or "I came to know."
J'ai su la nouvelle hier soir, par un ami commun.
I found out the news last night, through a mutual friend.
On a su qu'elle était enceinte au mariage de sa sœur.
We learned she was pregnant at her sister's wedding.
Comment est-ce que tu l'as su ?
How did you find out?
Plus-que-parfait
avoir (imparfait) + su
Si j'avais su, je ne serais jamais venu.
If I had known, I would never have come.
The fixed expression si j'avais su ("if I had only known") is the French equivalent of English regret-laden hindsight. It is everywhere.
Futur antérieur
avoir (futur) + su
Quand on aura su la vérité, on pourra avancer.
Once we know the truth, we'll be able to move forward.
Conditionnel passé
avoir (conditionnel) + su
J'aurais su quoi faire si tu m'avais prévenue.
I would have known what to do if you'd warned me.
The core uses
1. Know a fact
savoir + que + clause
This is the bread-and-butter use. Savoir introduces a fact through a que-clause.
Je sais qu'il est marié, mais je ne sais pas avec qui.
I know he's married, but I don't know to whom.
On savait depuis longtemps qu'elle voulait partir à l'étranger.
We've known for a long time that she wanted to go abroad.
After savoir used affirmatively, the que-clause takes the indicative. Savoir asserts a fact; the fact is real; no subjunctive.
2. Know how to (a learned skill)
savoir + infinitive
To express know how to do something — a learned skill, an acquired ability — French uses savoir + bare infinitive. No preposition.
Je sais nager mais je ne sais pas plonger.
I can swim but I don't know how to dive.
Tu sais cuisiner ? On cherche quelqu'un pour le repas.
Do you know how to cook? We're looking for someone for the meal.
Il sait parler quatre langues couramment.
He can speak four languages fluently.
This is one of the differences between savoir and pouvoir. Pouvoir is be able to (immediate possibility); savoir is know how to (acquired skill). Je sais nager = I have learned to swim; je peux nager = I can swim now (the pool is open, I have my swimsuit, etc.).
3. Know information (with a question word)
savoir + interrogative word + clause / infinitive
Used with si (whether), quand, où, comment, pourquoi, qui, quoi / ce que.
Je ne sais pas où il est parti.
I don't know where he went.
Tu sais comment ça marche ?
Do you know how this works?
On ne sait pas encore si la réunion aura lieu.
We don't know yet whether the meeting will take place.
Je ne sais pas quoi faire.
I don't know what to do.
4. Hedged / interrogative: subjunctive trigger
When savoir is negated or questioned with a que-clause that introduces a doubtful proposition, the subordinate clause may shift to subjunctive — though in modern conversational French, indicative is increasingly common.
Je ne sais pas s'il viendra.
I don't know whether he'll come. (Indicative — straightforward fact-checking.)
Je ne sais pas qu'il ait jamais accepté ce contrat.
I am not aware that he ever accepted that contract. (Formal/literary; subjunctive after negated savoir.)
In daily speech, the indicative is the default. The subjunctive after negated savoir is largely a written-register feature.
High-frequency idioms
- que je sache — as far as I know
- je ne sais quoi — a certain something (used as a noun: un je-ne-sais-quoi)
- Dieu sait — God knows (Dieu sait pourquoi)
- qui sait ? — who knows?
- en savoir long — to know a lot (il en sait long sur cette affaire)
- à savoir — namely (introducing a list)
- faire savoir — to let know (je vous ferai savoir)
- savoir faire — know-how (also a noun: le savoir-faire)
- savoir vivre — proper manners (le savoir-vivre)
- autant que je sache — as far as I know
Il a un certain je-ne-sais-quoi qui plaît à tout le monde.
He has a certain something that everyone likes.
On part à trois, à savoir Marie, Paul et moi.
There are three of us going, namely Marie, Paul, and me.
Qui sait ? Peut-être qu'il changera d'avis.
Who knows? Maybe he'll change his mind.
Comparison with English
Three friction points:
Savoir vs connaître. English know covers both. Savoir = facts, information, learned skills. Connaître = acquaintance with people, places, works. Je sais que Paris est la capitale (fact) ≠ je connais Paris (city). You cannot say je connais que — that's wrong.
Aspectual shift in passé composé. J'ai su is not "I knew" — it's "I found out." For "I knew" in the past, use je savais (imparfait). This trips up nearly every English-speaker the first time they encounter it.
No preposition before infinitive. Savoir
- bare infinitive: je sais nager, not je sais à nager or je sais de nager. Many learners want to insert a preposition.
Beyond these, savoir and know line up reasonably well — both express factual knowledge and learned skill.
Common Mistakes
Mistake 1: Using savoir for people or places.
❌ Je sais Paris très bien.
Wrong — for places, French uses connaître. Savoir is for facts about places, not the place itself.
✅ Je connais Paris très bien.
I know Paris very well.
Mistake 2: Using j'ai su to mean I knew.
❌ J'ai su qu'il viendrait.
Likely wrong — j'ai su means 'I found out.' For the stative 'I knew,' use the imparfait je savais.
✅ Je savais qu'il viendrait.
I knew he would come.
Mistake 3: Inserting a preposition before the infinitive.
❌ Je sais à nager.
Wrong — savoir takes a bare infinitive, with no preposition.
✅ Je sais nager.
I know how to swim.
Mistake 4: Confusing savoir and pouvoir for ability.
❌ Je peux conduire — j'ai pris des cours.
Possible but ambiguous: peux suggests 'I'm physically able right now.' For 'I have the skill / I learned to,' use savoir.
✅ Je sais conduire — j'ai pris des cours.
I can drive — I took lessons.
Mistake 5: Forgetting that the subjunctive stem is sach-, not sav-.
❌ Il faut que je save la réponse.
Wrong — the subjunctive of savoir is que je sache, with the irregular sach- stem.
✅ Il faut que je sache la réponse.
I need to know the answer.
Key takeaways
Savoir is the verb for knowing facts, information, and learned skills. It contrasts with connaître (acquaintance with people, places, works), and the contrast is non-negotiable. The conjugation has three irregular stems: sai-/sav- in the indicative, sau- in the futur and conditionnel, and sach- in the subjunctive, imperative, and present participle (sachant).
The most counter-intuitive feature for English speakers is the aspectual shift in the passé composé: j'ai su means "I found out," not "I knew." For "I knew," use the imparfait je savais. This shift mirrors the j'ai connu / je connaissais contrast for connaître.
Savoir takes a bare infinitive (no preposition) for learned skill: je sais nager. After affirmative savoir, the que-clause is in the indicative; after negated or questioned savoir, it can take the subjunctive in formal writing (the indicative is fine in speech).
Memorize the irregular stems, internalize the savoir/connaître split, and remember that j'ai su = "I found out." That's most of the verb mastered.
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