약 is medicine or medication. There is no difference. Medication should be accepted.
"Everyday" should be two words
Probably what the 약사s say the most.
이 藥은 每日 服用하세요
It's good to know Chinese character for Korean learning. You can see the nuance and meaning.
It's more common to use verb 복용하다 or 먹다 to talk about taking medication?
Is 약 the subject of the sentence, then? Because of the subject particle attached to it? Is this how all imperative sentences are structured, with the noun that the verb acts on being denoted with 는/은?
은/는 is the topic particle, not the subject one. So it's literally: "As for this medicine, take it every day." The speaker marks 약 as the central thing that they are talking about.
But why is it 은 instead of 을? 복용하다 is a verb right?
You can say '이 약을 매일 복용하세요' it's true you can say it like that. And also you can say '이 약은 매일 복용하세요' it's also a common expression. There is no need for use '은' instead of '을'. '복용하다' is a verb.
I'm just going to link to my comment on a similar exercise.
I am having some deja vu with my japanese lessons right now.