What is the difference between son and sa in french?

You're likely thinking of the French words "son" and "sa". They are both related to possession, but they have different meanings and uses:

Son means his or her and is used before a masculine noun.

* Son livre (his/her book)

* Son frère (his/her brother)

Sa means his or her and is used before a feminine noun.

* Sa maison (his/her house)

* Sa sœur (his/her sister)

Here's a breakdown:

* Son is used with masculine nouns like livre (book), frère (brother), chien (dog), jour (day).

* Sa is used with feminine nouns like maison (house), soeur (sister), voiture (car), nuit (night).

Let me know if you have any other questions!