zavet

1. vow; solemn pledge
   Monahinje daju zavet siromaštva. — Nuns take a vow of poverty.
   Dala je zavet da više neće pušiti. — She vowed never to smoke again.
2. (of the Bible) Testament
   Ta priča je iz Starog zaveta. — That story is from the Old Testament.
3. formal covenant; legacy
   Kosovski zavet je važan deo srpske tradicije. — The Kosovo Covenant is an important part of Serbian tradition.

Typical collocations are "dati/položiti zavet" (to take a vow) and "održati zavet" (to keep a vow).