Questions & Answers about Tvoj plan je gori od mog plana.
Why do we use od here, and what case does it take?
In Croatian, you can express 'than' in a comparison by using the preposition od followed by the genitive case. Because od literally means 'from', the sentence is structured like 'Your plan is worse from my plan'. That's why moj plan changes to the genitive form mog plana.
Where does the word gori come from?
Gori means 'worse' and is the comparative form of the adjective loš (bad). Just like in English, this comparative is completely irregular! It is in the masculine nominative case here to agree with the noun it describes, Tvoj plan.
Is mog a short form of another word?
Why are Tvoj and plan not in the genitive case like mog plana?
Tvoj plan is the subject of the sentence (the thing that is worse), so it stays in the nominative or 'dictionary' case. Only the part of the comparison that comes directly after od needs to change to the genitive case.