Le Présent: Savoir (to know)

Savoir is one of the two French verbs that English collapses into the single word know. Its companion is connaître (covered on its own page). The split between the two is one of the first major conceptual challenges for English speakers learning French — and unlike many tricky distinctions, this one is not a matter of style or register. Mixing them up produces sentences that are simply ungrammatical to French ears.

This page lays out the full paradigm of savoir, walks through its three core uses (knowing facts, knowing how, knowing information), surveys the most useful idioms (je sais pas, sache que, savoir-faire), and previews the savoir/connaître contrast that the dedicated page handles in depth.

The paradigm

Savoir is a 3e-groupe verb with two stems: sai- in the singular and sav- in the plural. The 3sg form sait ends in -t, which is the canonical 3sg ending for verbs in this family (il fait, il sait, il met, il prend, il doit).

Notice that the three singular forms (je sais, tu sais, il sait) all share the vowel /ɛ/, with the -s and -t silent. The plural forms shift to /a/ because the consonant v of the stem is now followed by a real vowel ending: nous savons /sa.vɔ̃/, vous savez /sa.ve/, ils savent /sav/. This pattern — singular forms ending silently, plural exposing a hidden consonant — is typical of 3e-groupe verbs.

Use 1 — Knowing a fact (savoir + que + clause)

The most basic use of savoir is to introduce a fact you hold to be true. The fact is expressed by a que-clause, identical in structure to English I know that...:

In speech, que is sometimes elided to qu' before a vowel: je sais qu'il..., je sais qu'elle.... This is mandatory in writing.

The verb in the que-clause stays in the indicative when the fact is presented as established. If savoir is negated or questioned (je ne sais pas si..., est-ce que tu sais si...), French speakers shift to si (whether) plus indicative — not subjunctive:

Use 2 — Knowing how to do something (savoir + infinitif)

Followed directly by an infinitive (no preposition), savoir means to know how to — that is, to have the skill or ability to perform an action. This is one of the cleanest distinctions between savoir and English can: where English uses can indiscriminately for both ability and possibility, French uses savoir for learned skills and pouvoir for circumstantial possibility.

The contrast with pouvoir is sharp: je sais nager means I have learned to swim and possess the skill. Je peux nager means circumstances allow me to swim right now (the pool is open, I'm not injured, etc.). A learner who says je peux nager meaning "I can swim" will be understood, but it sounds odd — French speakers hear it as "I'm able to swim right now" rather than "I have the skill of swimming."

Use 3 — Knowing information (savoir + interrogative)

When you know a piece of information — a name, a time, an address, a reason — you use savoir followed by an embedded question word: où, quand, comment, pourquoi, qui, ce que.

Note the use of ce que (what — as object) and ce qui (what — as subject) when the embedded question would use quoi:

This is not je sais quoi tu veux dire — that is ungrammatical. Quoi never appears as a direct object in an embedded clause; it is replaced by ce que.

Savoir vs connaître — the core split

The distinction is conceptual, not stylistic. Use savoir for:

• Facts (je sais qu'il vient)
• Skills / know-how (je sais nager)
• Information / data points (je sais où il habite)

Use connaître for:

• People (je connais Marc)
• Places (je connais Paris)
• Works of art, books, films, songs (je connais cette chanson)
• Subjects you have studied or are familiar with (je connais bien la philosophie grecque)

A simple test: if the object is a person, place, or work, use connaître. If the object is a fact, a skill, or an embedded question, use savoir. There is no overlap — these are not synonyms with subtle register differences. They are two verbs covering two different cognitive domains.

The pair shows up in a single sentence often enough that French speakers slot one in for the other instinctively. For learners, the rule of thumb is: savoir + clause/infinitif/question word; connaître + noun phrase referring to a person/place/thing.

The colloquial je sais pas

The phrase je ne sais pas is so frequent in spoken French that it has been worn down through repetition. In casual speech, the ne is dropped — je sais pas — and the je is often reduced as well:

• (neutral, written) Je ne sais pas.
• (informal spoken) Je sais pas. /ʒə sɛ pa/
• (very informal spoken) J'sais pas. /ʃɛ pa/
• (extremely casual) Chais pas. /ʃɛ pa/ — written this way only in dialogue or texting

These reductions are not slang; they are the actual default pronunciation of educated French speakers in informal settings. Learners who pronounce a careful /ʒə nə sɛ pa/ in everyday conversation will sound stilted.

In writing — even in informal email or texting — je sais pas is the most common form; j'sais pas and chais pas are reserved for transcribed dialogue or stylized casual writing.

The imperative — sache, sachons, sachez

Savoir has irregular imperative forms borrowed from the subjunctive. They are rare in everyday speech but appear in formal and literary registers, and in fixed expressions:

The most common use of these forms is sache que... / sachez que... meaning know that..., be aware that.... It is a slightly elevated register — found in formal letters, official notices, and dramatic speech, but not in everyday conversation:

In casual speech, you would replace sachez que with je vous informe que or simply au fait, ... (by the way). Save sache and sachez for formal writing or moments of deliberate elevation.

Useful idioms with savoir

A handful of fixed expressions with savoir are worth memorizing as units:

• savoir-faire (n.m.) — know-how, expertise, social skill
• savoir-vivre (n.m.) — good manners, knowing how to behave
• à savoir — namely, that is to say
• on ne sait jamais — you never know
• sans le savoir — without knowing it, unwittingly
• que je sache — as far as I know (always with subjunctive embedded structure)

A note on the passé composé

Although this page focuses on the present, learners often encounter a confusing fact early on: the passé composé of savoir (j'ai su) does not mean "I knew." It means "I found out" or "I learned" — the moment of acquiring the knowledge, not the state of holding it.

For "I knew" in the past (the ongoing state), French uses the imparfait: je savais. The same aspectual shift applies to connaître (j'ai connu = "I met for the first time"; je connaissais = "I knew, was acquainted with").

This shift is one of the most reliable transfer-error sources for English speakers, who default to the passé composé for any past event involving "knew."

Common Mistakes

Mistake 1: Using savoir with a person.

Mistake 2: Using connaître before a clause or question word.

Mistake 3: Inserting a preposition between savoir and the infinitive.

Mistake 4: Translating "I knew" as j'ai su.

Mistake 5: Using quoi instead of ce que in embedded questions.

Mistake 6: Pronouncing the silent endings.

Key takeaways

Savoir is the verb for knowledge that can be expressed as a fact (que-clause), a skill (savoir + infinitif), or a piece of information (savoir + question word). Its plural stem sav- contrasts with the singular sai-, and the imperative forms (sache, sachez) are borrowed from the subjunctive and appear mostly in formal writing.

The distinction between savoir and connaître is not optional or stylistic — it is grammatical. Learn both verbs together, drill the pairs side by side, and your savoir/connaître errors will fade within weeks of consistent input.