It's exactly as ricainrico says, with the exception that 'des' really is an abbreviation of 'de' + 'les' (which is mandatory: you can't write "de les" in French except for when 'les' is an object which is placed before the predicate in certain constructions (eg "C'était impossible de les empêcher")). "Les recettes des crêpes" means "The recipes of the crepes" (kind of like "The recipe that belongs to the crepes"). "Les recettes de crêpes" means "The crepes recipes".
Remember, des is a contraction and "contains" de+le. Try visualizing the sentence in English: "The recipes of crepes" - which is unconventional English, but not nonsensical - rather than "The recipes of the crepes", which you would normally follow by "that my mother used to make" or something. Hope that helps!
Frenchllama, in "mots des enfants" the des is possessive. in "recette de crepes" the crepes do not own the recipe. this should help: http://french.about.com/od/grammar/a/de-vs-du-de-la-des.htm i too was confused by the random use of des/de/du and this lesson helped alot.
Based on this, I'm having trouble understanding why "les mots des enfants" is correct (translating from "the words of children") instead of "de/d'enfants". Isn't the use of 'children' here general, and not specific (i.e. not "the children").
It's still not clear to me - the three examples used in explanations above all contain plurals (recipes, crepes). "The recipes of crepes" "The recipes of the crepes" "The crepes recipes" No one has (clearly) explained why apparently plural words are being given the singular 'de'. Short, simple sentences, with short, simple words would be appreciated.
@hirizvi Thanks for the link. Very helpful! @slurs From reading the link posted it looks like "de" is singular because of the following exception to the du (sg) / des (pl) rule: When the plural indefinite or partitive article is used with an adjective that precedes a noun, des changes to de. Examples: J'ai des amis. - J'ai de jeunes amis. I have some friends. - I have some young friends. (Note: J'ai un jeune ami. - I have a young friend.) J'ai mangé des épinards. - J'ai mangé de bons épinards. I ate some spinach. - I ate some good spinach. (Note: J'ai mangé de la bonne sauce des épinards. - I ate some good spinach sauce.)
Also, it is important to note that "des" denotes a specific noun. By saying "des crepes", you are saying "of the crepes", which implies that you have a specific set/type of crepes that you are talking about, that were probably mentioned beforehand. However, because you are talking about recipes for crepes in general, you use "de". In other words, these recipes are not of any specific crepes, but of the general idea of crepes. Understand? Hope this helps! I'm totally glad that you asked this question because it's helping me to articulate my own thoughts on this topic. I get kinda stumped by this grammar rule as well. Well, happy learning and God Bless!
ENatanael I think you confusing "les" plural definite article and "les" direct object pronoun... The first "les" is an article, "the" (plural) in english and the second "les" is a pronoun "them" in english... You can't say that it is an "exception" that when "les" is an object there is no abbreviation.. these are two distinct words, belonging to different grammatical categories...
@edu8: Yes, you are absolutely right. The two "les"s are however spelled and pronounced exactly the same and for someone learning French here on Duolingo without any prior knowledge of French grammar the two words are very hard to distinguish. I personally see it as one word which can take multiple forms. What I meant is simply that 'de' followed by 'les' almost always results in 'des'. You have to agree that 'des' is more common than "de les"?