The majority of French words derive from vernacular or "vulgar" Latin or were constructed from Latin or Greek roots. There are often pairs of words, one form being popular (noun) and the other one savant (adjective), both originating from Latin. Example:
~ brother: frère (brother) / fraternel
~ finger: doigt / digital
~ faith: foi (faith) / fidèle
~ cold: froid / frigide
~ eye: œil / oculaire
The French words which have developed from Latin are usually less recognisable than Italian words of Latin origin because as French developed into a separate language from Vulgar Latin, the unstressed final syllable of many words was dropped or elided into the following word.
It is estimated that 12 percent (4,200) of common French words found in a typical dictionary such as the Petit Larousse or Micro-Robert Plus (35,000 words) are of foreign origin. About 25 percent (1,054) of these foreign words come from English and are fairly recent borrowings. The others are some 707 words from Italian, 550 from ancient Germanic languages, 481 from ancient Gallo-Romance languages, 215 from Arabic, 164 from German, 160 from Celtic languages, 159 from Spanish, 153 from Dutch, 112 from Persian and Sanskrit, 101 from Native American languages, 89 from other Asian languages, 56 from Afro-Asiatic languages, 55 from Slavic languages and Baltic languages, and 144 from other languages (3 percent of the total).
French, like many other languages, possesses a continuum of several levels of register. The colloquial register is used in almost any circumstance of life, and should not be confused with slang or rude talk. Formal French is used in writing or in formal occasions (when people make official speeches or when they are interviewed on television, for instance). Some level of formality is also normally used in classrooms in France, although colloquial French is now spoken by more and more professors with their students.
Colloquial French differs from formal French in terms of grammar. For instance, the negation in formal French is "ne... pas", whereas in colloquial French it is simply "... pas", such as "I don't think so", which is "Je ne crois pas" in formal French, and "Je crois pas" in colloquial French. Another example of change in grammar is the way to ask a question: by inverting verb and subject in formal French, or also by using "est-ce que", whereas in colloquial French a question is phrased exactly as an affirmation, with the voice rising in the end. E.g.: "Is he sick?" would be "Est-il malade?" or "Est-ce qu'il est malade?" in formal French, and "Il est malade?" in colloquial French. On the other hand, questions with "est-ce que" are more colloquial than using inversion.
Secondly, colloquial French differs from formal French in terms of pronunciation. Some words undergo shortening, or sound change, whereas some syllables are dropped altogether. For instance, "yes" is "oui" in formal French, and becomes "ouais" in colloquial French; "I" is "je" in formal French, but becomes "j' " in colloquial French; so a sentence like "I think he'll come" is "Je pense qu'il viendra" in formal French, and "J'pense qu'i'viendra" in colloquial French. There are many instances of shortening of words, such as "teacher", which is "professeur" in formal French, but becomes "prof'" in colloquial French.
The French counting system is partially vigesimal: twenty (vingt) is used as a base number in the names of numbers from 70-99. So for example, quatre-vingts means 4 times 20, i.e. is the French word for 80, and soixante quinze (literally "sixty-fifteen") means 75. This is comparable to archaic English use of "score", as in "fourscore and seven" (87), or "threescore and ten" (70).
Belgian French and Swiss French are different in this respect.