Learn Hardcore Russian: Я забыл адрес магазина, поэтому не купил нужный журнал. - I forgot the store’s address, so I didn’t buy the magazine I needed.

In Russian, to show possession or “of the store,” you put магазин in the genitive case. The noun адрес (“address”) requires genitive for its object: адрес магазина = address of the store.

Why does журнал look like the nominative form even though it’s a direct object?

журнал is an inanimate masculine noun. In Russian, inanimate masculine singular nouns have the same form in the nominative and accusative. That’s why журнал (nom.) = журнал (acc.).

What does нужный mean, and why isn’t it нужного here?

нужный means needed or required. It modifies the direct object журнал (“magazine”). You don’t use нужного because that would be the genitive (or animate accusative). Here журнал is inanimate accusative, which looks like the nominative, so its adjective also stays in the nominative (нужный журнал).

What is поэтому, and how do I use it?