Grammatical agreement is a vast topic - and one of the banes of French students. While in English we have a few pronouns and adjectives that indicate gender and number (e.g., he/him/his and she/her/hers), in French, agreement is found in 5 of the 8 parts of speech.
There are three types of French articles (definite, indefinite, and partitive), and it's not always easy to know which one you need. Here's a detailed comparison to help you decide.
An article is a word that modifies a noun in a particular way, by stating whether the noun is specific, unspecific, or partial. There are three types of French articles, and they all agree in gender and number with the nouns they modify.
Contractions with de / à plus a definite article are not always required when the article is part of a proper noun, such as a city, title, organization, or surname.
The preposition de can be very difficult for French students, even at advanced levels. Knowing whether to use du, de la, or des rather than just de can be a real challenge! This lesson is a detailed explanation of when to use the preposition de all by itself and when to use the indefinite article, partitive article, or de + definite article (which looks like the partitive - but isn't. Ugh!)
The French definite articles (le, la, l', les) indicate either a particular noun or, contrarily, the general sense of a noun. They're used similarly to their English counterpart "the," but there are many instances where a definite article is required in French but not English.
Determiners are a category of grammatical terms that includes articles, numbers, and non-qualifying adjectives. Unlike qualifying adjectives, determiners serve two functions: they introduce and modify nouns at the same time.
With articles, the de vs du, de la, des choice has to do with affirmative/negative and whether there's an adjective in front of the noun.
The aptly named indefinite article (un, une, des) indicates an unspecific or unidentified countable noun.
There are three types of French articles (definite - indefinite - partitive). In negative constructions, two of them are usually required to change to de, meaning "(not) any."