Questions & Answers about Succesul este important.
Because Romanian usually puts the definite article at the end of the noun, not before it.
- succes = success
- succesul = the success
So -ul is the definite article here.
In a sentence like this, Romanian often uses the definite form to talk about a general idea or concept, especially with abstract nouns. So Succesul este important is a natural way to say that success, as a concept, is important.