you've probably learned this by now, but for others who may be wondering... nouns in swedish are either en words or ett words. Djur is an ett word. ett djur (an animal), djuret (the animal) and plural djur (animals) , djuren (the animals). So djuret is 'the animal' and djuren is 'the animals.
We don't have cases, and word order is pretty strict, so sometimes the category of definiteness helps us where other languages use other means to say things.
But maybe it's just a thing… it's like different languages are interested in different things. Like Russian is very interested in whether an action is finished or not. Swedish is very interested in whether the object we're speaking about is previously known to the other person or not.