All About Si

The French word si can be an adverb or a conjunction. Either way, si has several meanings and is used in numerous French constructions.

Si = if
Si is the French word for "if":

   Je ne sais pas si je veux y aller
   I don't know if I want to go

   Dis-moi si ça te conviendra
   Tell me if that will work for you

   Et si je ne suis pas fatigué ?
   And if I'm not tired?

   Si j'étais riche, j'achèterais une maison
   If I were rich, I would buy a house
   (lesson on si clauses)

Si = so
Si can be used as an intensifier:

   Je suis si fatigué
   I'm so tired

   J'ai si faim
   I'm so hungry

   Je ne savais pas qu'il était si mignon
   I didn't know he was so cute

Si = as, so
Si can make a comparison:

   Il n'est pas si intelligent qu'il pense
   He's not as smart as he thinks

   Ce n'est pas si facile
   It's not as easy as that, It's not that easy

Si = while, whereas
Si can put two clauses in opposition:

   S'il est beau, sa femme est laide
   Whereas he is handsome, his wife is ugly

   Si tu es gentil, ton frère est méchant
   You're kind, while your brother is mean

Si = however, no matter how
Si can be followed by a subjunctive clause to express a concession:

   Si beau qu'il fasse, je ne peux pas sortir
   No matter how nice the weather is, I can't go out

   Si gentil que tu sois, je ne t'aime pas
   However kind you are, I don't love you

Si = yes
Si means "yes" in response to a negative question or statement:

   Tu ne vas pas venir ? Si (je vais venir)
   You're not going to come?

Yes (I am going to come)

   N'as-tu pas d'argent ? Si, j'en ai
   Don't you have any money? Yes, I do

   Jeanne n'est pas prête. Si, si !
   Jeanne isn't ready. Yes (she is / I am)!

Si = did I hear correctly, is this what you're asking?
If someone asks a question and you're not sure (or can't believe) you heard correctly, you can request confirmation or clarification by repeating what you did hear with the word si:

   Si j'ai faim ?
   (Are you asking) if I'm hungry?
   (You couldn't really hear the question)

   Si je veux quoi ?
   You're asking if I want what?
   (You're not sure you heard correctly; you heard "Do you want a free TV?")

   Si j'ai combien d'enfants ?
   You're asking if I have how many kids?
   (You didn't hear "how many," or you heard "Do you have 7 kids?")

Et si = what if, how about
In informal French, et si is often tacked on the beginning of a suggestion (with the verb in the imperfect):

   Et si on allait au ciné ?
   How about going to the movies?

   Et si tu amenais ton frère ?
   Why don't you bring your brother?