Learn French: À la convention, nous avons découvert ce sur quoi se base le livre. - At the convention, we discovered what the book is based on.

When "what" means "the thing that" and works with a preposition (like sur), French uses the structure ce + preposition + quoi. Think of ce as "the thing", sur as "on", and quoi as "which". Since the verb phrase is se baser sur (to be based on), "what the book is based on" becomes "the thing on which the book is based": ce sur quoi.

Why is the word order se base le livre instead of le livre se base?

This is a stylistic inversion. In relative clauses (like those starting with où, que, or ce sur quoi), if the subject is a noun like le livre rather than a pronoun like il, it is very common to put the subject after the verb because it flows better to the French ear. However, saying ce sur quoi le livre se base is also completely correct!

Why use the reflexive verb se base instead of est basé?

Both se baser sur and être basé sur mean "to be based on" and can be used interchangeably here. French frequently uses reflexive verbs (with se) to express a passive idea, especially when the subject is an inanimate object.

Is the word convention a "false friend" in French?