napola

1. half; partly
   Vrata su bila napola otvorena. — The door was half open.
   Posao je tek napola završen. — The job is only half done.
2. (of dividing) in half; in two
   Preseci jabuku napola i daj meni jednu polovinu. — Cut the apple in half and give me one half.
   Račun smo podelili napola. — We split the bill in half.

The adverb is written as one word: napola. Separate "na pola" is the preposition with the noun pola in constructions such as na pola puta, na pola sata.