kopča

1. clasp; buckle; fastener
   Pukla mi je kopča na kaišu. — The buckle on my belt broke.
   Ne mogu da otvorim kopču na ogrlici. — I can't undo the clasp on my necklace.
2. (for hair) hair clip
   Kupila sam novu kopču za kosu. — I bought a new hair clip.
3. (figurative) link; connection
   Ovaj most je kopča između dva dela grada. — This bridge is the link between two parts of the city.

A hair clip is also often called «šnala» in everyday speech.