Possessives in the Accusative Case
When possessive determiners (my, your, his, etc.) describe the direct object of a sentence, they must be in the accusative case. The ending they take depends entirely on the gender of the noun and whether it is "animate" (alive).
Feminine Objects
Feminine nouns change their -a ending to -u in the accusative. Possessive determiners do exactly the same. For example, tvoja (your) becomes tvoju, and vaša (your, plural/formal) becomes vašu.
Masculine Inanimate and Neuter Objects
If the object is a neuter noun or an inanimate masculine noun (a thing or a concept, rather than a person or animal), the accusative form is identical to the nominative (dictionary) form. The possessive determiner doesn't change at all.
Notice how these endings combine in a sentence with multiple objects of different genders:
Masculine Animate Objects
When the direct object is an animate masculine noun (like a person or an animal), the rules change. The noun gets an -a ending, and the possessive determiner takes an -eg (or sometimes -og) ending. For example, tvoj (your) becomes tvojeg.
