Spot the Mistake in 'Parlez-Vous Français'

What's wrong with the French phrase Parlez-vous Français? That's an easy one: It contains a spelling error. It should be written: Parlez-vous français? with a lowercase f in français. Here's why. 

The French word français has three English equivalents: two nouns (French the language and French the nationality or person) and French the adjective. All three forms are capitalized in English.

In French, however, français is only capitalized when it is used as a noun identifying a nationality, such as the following: Les Français aiment le vin (The French like wine). When français is used as an adjective or refers to the language, however, the f is lowercase, not capitalized: J'aime le vin français (I like French wine).

Many beginning French students make this mistake, as do many Francophones who speak English well. They capitalize français, espagnol, and the like, whether the word is a noun, adjective, or language because nationalities and languages are always capitalized in English.

Likewise, the names of all languages are lowercase, as with l'anglais, le portugais, le chinois, l'arabe, l'allemand, le japonais, le russe, etc.

For French nationalities, the proper noun and adjective are spelled exactly the same, but the proper noun is capitalized, while the adjective is not capitalized. Thus, in French we write: 

• un type américain (adjective) = an American guy
  BUT un Américain (noun identifying nationality) = an American 
• Elle aime la cuisine espagnole. (adjective) = She likes Spanish food/cuisine.
  BUT Elle s'est mariée avec un Espagnol. (noun identifying nationality) = She married a Spaniard.
• J'ai vu un animal mignon australien. (adjective) = I saw a cute Australian animal. 
  BUT J'ai vu un Australien. (noun identifying nationality) = I saw an Australian.

• Un Français = a Frenchman
• Une Française = a French woman
• Les Français = the French people, the French OR Frenchmen
• Les Françaises = French woman
• Le Français n'aime pas... = The average Frenchman or French person doesn't like ...
• Le français = the French language
• parler français = to speak French
• en bon français = in proper French
• le français courant = fluent French
• Il parle français couramment. = He speaks French fluently.
• à la française = French or French-style; (in) the French way
• Territoire français des Afars et des Issas = French Territory of Afars and Issas
• le français seconde langue = French as a second language
• un leçon de français = a French lesson
• un cours de français = a French course
• une faute de français = a grammatical mistake in French
• écorcher le français = to speak terrible French
• chez les Français = among the French
• faire du français (...en s'amusant, ...en maternelle, etc) = to do French or the French way (...in having fun, ...in nursery school, etc.)
• le mal français = main issues of French society, problems of France