popuna

1. (of positions, places) filling
   Raspisan je konkurs za popunu radnih mesta. — A competition has been announced to fill the vacancies.
   Popuna kadrova u bolnici ide sporo. — Staffing the hospital is going slowly.
2. (of stocks, supplies) replenishment
   Prodavnica čeka popunu zaliha. — The shop is waiting for its stock to be replenished.

For filling in a form, popunjavanje is usually used rather than popuna.