Could someone explain the structure of this sentence, and why it wouldn't be something like, "Skriver bruker du brev?"?
We do have a verb for this, and it's pretty common: tend. I don't know why Duo doesn't accept it! I tend to write letters is a perfectly good and ordinary English sentence, and as far as I can make out it has the same meaning as jag brukar skriva brev - unless there's some subtlety to brukar that I'm missing.
I'm not sure where exactly we learned what a model verb is. It is hard when they don't even teach us sentence building in English class to grasp the terms here! I know my French sentence building, however. I don't get it. Brukar is this modal verb, but it is skriva you are changing, so does the list of "does not need att" mean that the verb itself (on the list) requires no att, or that words use with the words on the list require no att? I'm not sure I explained my question right. I'm having trouble asking it.
We usually send people off to this topic, did you read it? https://www.duolingo.com/comment/7075383
This is Infinitive 1 and the modal verbs aren't taught until a little later, which isn't optimal of course. So unless you're backtracking, you won't be able to access this yet: https://www.duolingo.com/skill/sv/Verbs:-Modal
There it says that
Modality is what allows us to attach things such as belief, attitude, and obligation to statements. This means that words such as must, may, want, are all modal verbs.
Then it goes on to compare things like I eat and I want to eat. If you're saying I eat, that's just a fact, but I want to eat is an attitude already, so that's what modal verbs are. – After verbs like this, you can't have att before another verb in the infinitive. So we say Jag måste läsa, but if you add att in between there, it'll just be wrong.
But then there are many cases where both ways are possible. In point 3 in the post by Zzzzz... , you can add att if you want to.
Another way of putting it: An infinitive usually go together with 'att' (att gå, att åka, att äta). But if the infinitive is preceeded by a modal verb the 'att' is dropped: Jag måste gå, Jag ska åka, Jag vill äta (no 'att' is dividing the two verbs). Hope this helped you?!
The comments below suggest that "Brukar du + infinitive?" should not be rendered as "Are you used to + infinitive?" So how about: "Is it usual for you to write letters?" Could this be an acceptable translation? I know my sentence starts looking passive, but I do like the idea that "brukar" could be translated as a verb phrase rather than as an adverb...