Learn Romanian: Am nevoie de ciocanul tău ca să repar ușa. - I need your hammer to repair the door.

The phrase am nevoie literally means "I have need". In Romanian, you always use the preposition de (of) to connect it to the thing you need, making it literally "I have need of your hammer".

Could I say îmi trebuie instead of am nevoie de here?

Yes, you could say îmi trebuie ciocanul tău. Both mean "I need your hammer". The difference is grammatical: îmi trebuie uses a dative pronoun (literally "your hammer is necessary to me") and drops the de.

Why does ciocan have the -ul ending before tău?

In Romanian, when a possessive adjective like tău (your) follows a noun, that noun must take a definite article. Because ciocan (hammer) is a neuter noun, it takes the singular definite article -ul, making it ciocanul tău (literally "the hammer your").

What is the difference between using ca să and just să before repar?

While both can translate to "to", ca să specifically means "in order to" and strongly emphasizes the purpose of your action. Using just să is also grammatically correct here and very common in everyday speech.