napor

1. effort
   Uložili smo mnogo napora u ovaj projekat. — We put a lot of effort into this project.
   Uprkos svim naporima, nismo uspeli. — Despite all our efforts, we didn't succeed.
2. (of the body) exertion; strain
   Doktor mu je zabranio fizički napor. — The doctor told him to avoid physical exertion.

Typical collocations: "uložiti napor" (to make an effort), "uz veliki napor" (with great effort).