In French, two irregular verbs express “to know”: connaître and savoir. Connaître means “to know” in the sense of being acquainted with someone or something. Use the verb connaître when you can substitute the words “to be familiar with”:
- Je connais Luc. (I know Luke [meaning: I am acquainted with Luke].)
- Je connais cette chanson. (I know this song [meaning: I have heard this song before or I am familiar with this song].)
Savoir means “to know” in the sense of knowing how to do something or knowing something by heart, through mental ability or through a learning process. Savoir expresses the knowledge of facts or reasons about certain things:
- Je sais danser. (I know how to dance.)
- Je sais cette chanson. (I know this song [meaning: I can sing the words].)
- Je sais ton adresse. (I know your address.)
Savoir is used:
To express know‐how or the lack thereof.
- Il sait lire mais il ne sait pas écrire. (He knows how to read, but he does not know how to write.)
In the passé composé to express “to find out” or “to learn about something.”
- Je l'ai su hier. (I found out about it yesterday.)
Idiomatically in the conditional to express “could” or “would.”
- Il ne saurait pas cacher son bonheur. (He couldn't hide his happiness or He wouldn't be able to hide his happiness.)