upotrebljavati

1. to use
   Ovu reč mladi retko upotrebljavaju. — Young people rarely use this word.
   Svakog dana upotrebljavam laptop za posao. — I use my laptop for work every day.
2. (of substances) to take; to use
   Da li upotrebljavate neke lekove? — Are you taking any medication?

The perfective is upotrebiti; in everyday speech koristiti is more common.