Circumflex

The circumflex (^), also known as the caret, is a diacritic used in French and a few other languages. It is like a little hat over a vowel. Originally, the circumflex was an acute accent and a grave accent put together.
In French, the circumflex usually shows the loss of letter, usually the loss of the letter S. Example: maistre (Middle French) &gt; maître (modern French). From here, its function is historical.
Also, less often, the circumflex is used to distinguish between homophones. These are words spelt the same, but with different meanings. Example: "sur" = on, but "sûr" = safe or certain. In those cases the pronunciation of the two words may be different.