Learn Russian: Тётин сын хочет стать врачом после университета. - Aunt's son wants to become a doctor after university.

Both тётин сын and сын тёти mean "the aunt's son" and are grammatically correct. However, for close relatives and names (like мама, папа, тётя), conversational Russian strongly prefers using these special possessive adjectives ending in -ин. In this sentence, тётин acts like an adjective that matches сын in gender, number, and case (masculine, singular, Nominative).

Why is the word for doctor in the Instrumental case (врачом)?

The verb стать (to become) requires the noun that follows it to be in the Instrumental case. This is a very common pattern you will see whenever someone talks about transitioning into a new profession, role, or state.

Why does the Instrumental ending for врач use -ом instead of -ем?

This is due to a specific spelling rule. After "hushing" consonants like ч, the Instrumental masculine/neuter ending depends on where the stress falls. If the ending is stressed, it takes -ом (врачо́м). If the stress falls on the root of the word, it takes -ем (like in му́жем).

Why does the word for university have an -а at the end (университета)?