"The knights love the woman."
Translation:Azantyssy ābre jorrāelzi.
I'm not an English native myself, so I don't know how this is taught in English schools. And since the English language doesn't really use noun declensions all that much (which is partly why it is such an easy language to learn), this might be a bit of a strange concept to wrap your head around.
Basically, a noun changes appearance in the context it is used. For example, in English, the nominative singular is "knight", but the nominative plural is "knights". The noun has already changed. Or it might be in the genitive form ("knight's"). But those are almost all declensions that the English language knows.
In High Valyrian, like many other languages, a noun changes form for almost every case it can be.
The nominative is used in the subject of the sentence. In this case, "azantyssy" is the subject, because the knights are the ones that "do" the loving. Thus, we use a nominative form. You can usually find out what the subject is by seeing what the predicate is referring to ("jorrāelzi" in this case), and that's the knights.
The accusative is one way to mark objects of a sentence as such. English doesn't change the noun for the accusative anymore, but this declension is still there in the word "whom", so while you would ask for the subject with "who", you could ask for an object in the accusative case with "whom".
In the case of this sentence: "Who" is doing the loving? The knights, so knights have to be in nominative form. "Whom" do they love? The woman. So the woman needs to be in accusative form (which is ābre).
This might be a bit intimidating at first, but High Valyrian has a total of 8 cases, and you can find how they change appearance here: https://wiki.dothraki.org/High_Valyrian_Noun_Declensions