One of the most common questions I see on the English-to-French Duolingo is whether the definite article (le/la/les), partitive article (du/de la), or plural indefinite article (des) should be used. This confusion arises because you can omit articles in English, but you usually cannot in French.
Here are some guidelines on how you can use articles correctly on Duolingo. Note that native Francophones may use them differently, but Duo is very specific about their usage.
When you see an article, translate it directly. "The" will always be definite, "a" will always be indefinite (un/une), and when you see des in French, you can use "some" or just omit it in English. (There are exceptions. See below.)
When articles are missing in an English sentence, they must be added to the French translation. The definite article can be used if one of three conditions is met:
When referring to particular nouns that are known to the speakers.
Before the subject of a sentence to state general truths about it.
Before the direct object of a verb of appreciation (like aimer) to express like/dislike.
If any of the above is true, then use the definite article. Otherwise, use the indefinite or partitive, depending on whether or not the noun is countable. In most cases, use du or de la (partitive) for singulars and des (indefinite) for plurals.
I like wine, but I am drinking milk. — J'aime le vin, mais je bois du lait.
Both articles are missing in the English version of this example. Aimer expresses fondness for wine, so le vin should be used there. However, boire is not a verb of appreciation, so the partitive du should be used on the uncountable lait.
Cats are animals. — Les chats sont des animaux.
This is a general truth about cats, but #2 above can only apply to subjects, so only chats takes a definite article here. Animaux are countable, so the indefinite is used.
He likes to eat meat. — Il aime manger de la viande.
This is a tricky example because meat is the direct object of manger, not aimer. Thus, #2 does not apply and viande cannot take a definite article.
Here's another example: "Local women wear black dresses." Which articles should we use? Think about it for a moment. The correct answer is at the bottom.
Also remember:
In negations, indefinite and partitive articles all become de except with être or if you want to stress the negative aspect.
For countable nouns, sometimes "some" should be translated as quelque or certaines. These words denote some subset of a larger group.
If there's an adjective in front of the noun, des becomes de.
If you want to learn more about the partitive, look here.
Local women wear black dresses. — Les femmes locales portent des robes noires.
This sentence is making a generalization about local women, so femmes takes the definite article. Robes noires does not, however, because it's not the subject nor the object of a verb of appreciation. However, consider this similar example where les can be used on both:
Local women like black dresses. — Les femmes locales aiment les robes noires.
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