The term RING UNIT is composed of two crossword solutions: CARAT and ROUND. A CARAT is a unit of measurement used to measure the weight of diamonds and other precious stones, and is equal to 0.2 grams. A ROUND is a shape that is circular in nature, and is often used to describe the shape of a diamond or other gemstone. Together, these two terms form the term RING UNIT, which is used to describe the combination of a diamond or other gemstone and its setting in a ring.