vitalan

1. (of a person) vigorous; energetic; full of life
   Deda mi je i u osamdesetoj veoma vitalan. — My grandpa is still very vigorous at eighty.
2. (usually definite form) vital; essential
   Srce i pluća su vitalni organi. — The heart and lungs are vital organs.
   Voda je vitalni resurs za ceo region. — Water is a vital resource for the whole region.
3. (of a plant, organism) hardy; sturdy
   Ova sorta je vitalna i podnosi mraz. — This variety is hardy and tolerates frost.

In the sense "essential" the definite form is usually used: vitalni organi, vitalni interesi.