Cases of word usage

1) the least valuable piece; to deposit (clothing, jewellery etc) as security for money borrowed (pawn)

2) a silvery-white or bluish-white round deposit found inside the shells of some oysters, valued as a gem (pearl)

3) one of the thin pieces of hard material that cover the skin of many fish etc; the chalky deposit inside kettles, water-pipes etc; a simple balance or instrument for weighing by comparing something with a known mass; any machine used for weighing (scale)