Learn Hardcore Latin: Soror discipuli eum videt. - The student's sister sees him.

In Soror discipuli eum videt, discipuli is in the genitive case to show possession. It literally means the sister of the student. If it were nominative (discipulus), that would indicate the student as the subject, which is not the intention here.

Who or what does "eum" refer to in this sentence?

Eum is a third-person masculine singular pronoun meaning him. In this context, eum is referring back to the same discipulus mentioned in the genitive form. So Soror discipuli eum videt means The student’s sister sees him.

Why is "videt" used instead of "video" or "vides"?

Videt is the third-person singular active indicative form of the verb vidēre (to see). The subject is soror (sister), so the verb must be videt (she sees). If you were saying I see, you’d use videō, and for you see, you’d use vidēs.

Does Latin word order matter as much as in English, and could we rearrange this sentence?

Latin word order is more flexible than English due to the case endings that clarify the grammatical roles of words. You could rearrange this sentence to something like Eum soror discipuli videt or Soror eum discipuli videt and still convey the same meaning. However, Soror discipuli eum videt is a clear, straightforward arrangement.