My, your, our, their — and the agreement game
In Russian, 'my' has four forms — masculine, feminine, neuter, plural — and they must match the noun they describe. Same for 'your', 'our'. The third-person possessives ('his', 'her', 'their') do not change.
First and second person possessives
These four words follow the same shape: мой / твой / наш / ваш + endings. My: мой (m), моя (f), моё (n), мои (pl). Your (informal sg): твой, твоя, твоё, твои. Our: наш, наша, наше, наши. Your (formal/plural): ваш, ваша, ваше, ваши.
Third person — invariable
His: его (pronounced 'ye-VO' — the г is silent, a 'в' sound replaces it). Her: её ('ye-YO'). Their: их ('ikh'). These never change form. Его книга (his book), его дом (his house), его друзья (his friends) — all the same его.
Matching the noun, not the speaker
The agreement matches the gender of the thing owned, not the owner. So even if a man is talking, if he's talking about his book (книга, feminine), he says моя книга.
When you can drop it
Russians often drop possessive pronouns when context makes them obvious — especially with family members. Это мама usually means 'This is my mom' in conversation.
