It's important to write a letter with the correct accent as somethimes it could have a completely different meaning. The two most common mistakes made by beginners are related with the accents for:
- a and à
- ou and où
a is the conjugated form of the verb "avoir" (to have) when conjugated with "il, elle, on".
à is the preposition meaning "to".
ou means "or".
où means "where".