The circumflex, aka "little hat," is the only French accent that may be found on any of the five vowels. In any given word, the circumflex may serve one or more purposes.
Contractions occur when two words are combined into one, sometimes with a distinctly different spelling. In English, contractions like "won't" are optional and indicate informality. In French, however, contractions are required, regardless of the register you're speaking or writing in.
An elision is a type of contraction that occurs when two words are combined: one or more letters are dropped and replaced with an apostrophe. In French, written elisions are required, regardless of the register you're speaking or writing in.
French grammar is sometimes trumped by pronunciation, as in the case of euphonic adjectives. Because French does not like the hiatus created when a word ending with a vowel precedes a word that begins with a vowel or mute h, a few adjectives change their spelling—and thus their pronunciation—for purely euphonic reasons.
In both French and English, there's a lot of overlap between fractions and ordinals: the vast majority of these two types of numbers share the same word. In English, they are identical from "third" on up, while in French they're the same starting with cinquième.