General niceness:
* Miły/miła (masculine/feminine) - This is the most common and direct translation, meaning "nice" in a general sense.
* Sympatyczny/sympatyczna (masculine/feminine) - This means "pleasant" or "likable", and is often used when describing someone's personality.
* Fajny/fajna (masculine/feminine) - This is a more informal and colloquial way of saying "nice", often used for things or situations.
Other meanings of "nice":
* Ładny/ładna (masculine/feminine) - This means "pretty" or "beautiful" and is used for objects or people.
* Dobry/dobra (masculine/feminine) - This means "good" and can be used in some contexts where "nice" would be appropriate.
The best way to choose the right translation depends on the context and the desired level of formality.