"The girl is wearing a dress."
Translation:Jenta har på seg kjole.
That I know, I should have been more clear. I meant the article of kjole, as one acceptable translations was Jenta har på seg kjole.
I thought we'd only do that in plural, or when talking about something more general. But in this case, it seems to be pretty specific, i.e. she is wearing a dress in this moment.
Oh, ok! In many sentences, you can choose wether you want the article or not. "Jenta har på seg (en) kjole", "Han er elev" vs "Han er en elev". It doesn't change the meaning much. It might put more emphasis on the dress etc if you keep the article, and be a more general statement if you don't.
I asked my wife (native speaker) about this and she said she would use "en kjole" rather than just "kjole" in the following way. "En kjole" = A dress, in the sense that this is the specific thing she is wearing. "Kjole" = The category of clothes "dresses" as opposed to some other thing like pants or leggings or something. It is a suble change, but dropping the "en" makes it a much more general statement.