Accents
Acute
The acute accent (l'accent aigu) is only used with the letter e to mark the /e/ sound. (see Vowel Sounds: [e] vs [ɛ]).
Dieresis
Also known as le tréma in French, the dieresis (those two dots ¨) is a punctuation mark placed over a vowel to indicate it should be pronounced separately from a neighboring vowel. Normally, the letter combination "ai" makes a single sound but with the dieresis on the "i," it becomes "ai" with two distinct vowel sounds, as in "maïs".
Grave Accent
As we saw on (see Vowel Sounds: [e] vs [ɛ]), the grave accent (l'accent grave) when placed over an e indicates a /ɛ/ sound.
It is also placed over a and u in a small number of words:
In a few cases, the grave accent serves to distinguish two words which otherwise would have the same spelling.
When appearing over the letter e, it causes final syllables to be pronounced as [ɛ] as opposed to [e] (ie. dès vs des). (see Vowel Sounds: [e] vs [ɛ]).
Circumflex
The circumflex accent (^) (L'accent circonflexe) - that little hat over vowels (î, â, ê) - is silent in French, and some reformers have called for its abolition. In some cases the circumflex marks the location of an s that existed in the original latin word such as "forestis" which became "forêt".