I think it works like this: Verbs that require naar (for) with a noun can't take om te ([for] to) constructions directly.
Example (normal verb):
- Ik verlang water. - I want water.
- Ik verlang om water te drinken. - I want to drink water.
Example (phrasal verb):
- Ik verlang naar water. - I long for water.
- Ik verlang ernaar om water te drinken. - I long for drinking water.
Think of verlangen naar as a phrasal verb based on, but separate from, the verb verlangen. It translates quite literally to long for. When you substitute the phrase drink water for the noun water, such a phrasal verb behaves quite differently from a normal one:
- I want water. → I want to drink water.
- I long for water. → I long for drinking water.
It would be wrong to say "I want drinking water" or "I long for to drink water", though I think the latter would have been correct in Shakespeare's time.
Dutch has the same problem and solves it in a more straightforward but clumsier way:
- Ik verlang water. → Ik verlang om water te drinken.
- Ik verlang naar water. → Ik verlang ernaar om water te drinken.
The problem I mentioned is that after verlang naar / long for we need a noun, but om water te drinken / to drink water is more similar to a subordinate clause than a noun. The modern English solution is to use the gerund construction drinking water, which can more readily replace a noun. The Dutch solution is basically to add het / it, which can then be described by the phrase om te drinken. This is a bit obscured because the subsequent transformation naar het → ernaar (for it → therefore) makes the words naar and het disappear. The following overly literal translations should be helpful:
- Ik verlang ernaar om water te drinken. - I long for it, to drink water.
- Jullie verlangen ernaar om te zingen. - You long for it, to sing.
I have added commas because one occasionally sees this construction in English from my fellow German speakers - almost always with the comma, because it would be required by German rules. (The commas also prevent reading the sentence as perfectly grammatical English sentences with an entirely different meaning.)
No, that would just be: "Ik wil je eten eten."
There are several tricky nuances here in which Dutch, English and German differ. As is often the case, it makes sense to look at the other two languages in relation to German, the most conservative of the three languages:
- English often has an extra to that goes with infinitives, when compared to Dutch and German. (I.e. Dutch and/or German don't use the respective translations te and zu in the same situation.)
- Dutch often has an extra om that goes with infinitives, when compared to English and German. (I.e. English and/or German don't use the respective translation in order to and um zu in the same situations, but merely to and zu.)
Here in particular, we need to distinguish the verb willen and the closely related noun wil:
- Ik wil iets doen. - Ich will etwas tun. - I want to do something.
- Ik heb de wil om iets te doen. - Ich habe den Wunsch, etwas zu tun. - I have the will to do something.
In the first case (verb willen), English has the extra to. In the second case (noun wil), Dutch has the extra om.
Here is how you could have guessed that Dutch doesn't add om te (or even te) in your example. To get an intuition, we shouldn't use the English translation of willen, which is want, but the English cognate, which is will. Despite the difference in meaning, I think "Ik wil om je eten te eten" is ungrammatical for the same reason that "I will to eat your food" is ungrammatical: om te or to isn't added with auxiliaries, even if it would make sense semantically.
The trick is, of course, realising that the right intuition comes from the English sentence with will, not the proper English translation.
Yes and no. What happened is that since the time when English and Dutch/German were all a single language, whatever people would have said at the time has evolved in different directions. Sometimes words move into new semantic fields and get replaced by other words in their old semantic fields. So the cognates have slightly different meanings. And sometimes words move from one grammatical category to another. Both events are basically independent, and rare enough so that they seldom occur together. Here only the first thing happened.
Of course we normally need to translate the words, not find the cognates. And normally this gives us all the right intuitions. But on occasion, as in this example because the cognate of willen is an auxiliary but the English translation is a full verb, using the cognates instead can give additional insight.
Or think of it this way: For an English speaker learning Dutch, it is natural to speak English Dutch as a first approximation: English with all the English words replaced by their Dutch cognates. (This is how we learn dialects of our own native language, and it also works quite well for closely related languages.) Conversely, for a Dutch speaker learning English it is natural to start with Dutch English.
Now the trick is, when learning Dutch, to start not just with English Dutch (which obviously is much easier to learn than proper Dutch), but also with Dutch English, i.e. Dutch word order applied to the English cognates of the correct Dutch words. (Using the English inflections, not the Dutch ones, because the English inflections are usually the cognates of the Dutch ones.) The latter means speaking English like a Dutch speaker with a very poor command of English grammar and the typical traps for Dutch speakers.
- English: I want to eat your food.
- English Dutch: Ik wens je eten te eten. (This is actually correct and means "I wish to eat your food.")
- First attempt at Dutch English: I will to eat your eating.
- Correct Dutch English: I will eat your eating.
- Dutch: Ik wil je eten eten.
For Dutch English we need to know that the Dutch translation of want is willen and the English cognate of willen is will. The Dutch translation of food is eten and the English cognate of that is eating. Of course the Dutch translation of to is te, and the cognate of te is to. However, we can see that the resulting sentence "I will to eat your eating" is not grammatical. This shouldn't be the case because Dutch English, while often semantically odd and expressing unintended things, is normally grammatically correct English. (There are some regular exceptions such as word order, which always need to be fixed first - as I have done above.) But fortunately we can use our intuitions from English grammar to see that we just need to remove to to make the sentence grammatical.
Again in different words:
Our first guess was that a poor English speaker from the Netherlands would say "I will to eat your eating". But the languages are so closely related that they wouldn't actually make the odd mistake of the extra to. So they would really say "I will eat your eating", and this tells us precisely what the correct Dutch sentence is.
This method may appear weird at first, but it is really quite powerful as it makes full use of your skills in English grammar to learn Dutch grammar quickly and intuitively.
Should you look at all sentences like that? Certainly not if it slows you down. But doing this occasionally will improve your intuitions for Dutch grammar and will make some of them appear as natural to you as native speaker intuitions do. You are basically getting grammar for free!
Let's look at what the two forms of verlangen mean:
- iets verlangen = to want/demand something
- naar iets verlangen = to long/pine/crave for something.
Clearly demanding (a parrot) is not the same concept as pining (for the fjords).
Fortunately, these are good translations that render accurately the critical factor which triggers the difference: the preposition naar = for. This accuracy makes it much easier to see what's going on, because it's almost completely parallel in both languages. We can say this:
- Ik verlang om te zingen. - I demand to sing.
But we cannot say this:
- ( * ) Ik verlang naar om te zingen. - ( * ) I pine for [to] sing.
It's ungrammatical in both languages for the same reason. One solution involves a gerund:
- Ik verlang naar zingen. - I pine for singing.
While this works in both languages, there is also another option: adding expletive it, i.e., the meaningless it that is well known from it is raining:
- (*) Ik verlang naar het om te zingen. - (?)I pine for it to sing.
This sounds so inelegant in English that it's almost wrong. (To make things worse, there is also the unintended interpretation in which it is not expletive but refers to a bird.) And I think in Dutch it's even worse. But in Dutch we can fix it by applying the general rule that naar het = for it is (almost) always replaced by ernaar = therefore:
- Ik verlang ernaar om te zingen. - (*) I pine therefore to sing.
While ernaar can be used with all pronouns, it takes the emphasis off them and is particularly suitable for expletive pronouns. This is why it has made our strange previous sentence perfectly acceptable.
It is only this last step where the two languages diverge. English has almost lost therefore (though it has survived in formal language), but Dutch has generalised use of its cognate ernaar so much that it can rescue our construction.