Karat
kar·at | ˈker-ət
noun
A unit of fineness for gold, equal to 1 part of pure gold in an alloy
Karat is specifically used as a unit of fineness when measuring gold. A single karat is equal to 1 part of pure gold in an alloy, with pure gold being designated as 24K. This type of gold is considered too soft for jewelry except in specific instances when it is purely decorative. For this reason, different types of jewelry are often rated at different karats. For example, the standard fineness in the United States for gold jewelry is 14K, meaning there are fourteen parts pure gold and ten parts base metal in the piece. Rings are often rated at 10K to ensure a higher level of durability in the piece, while the highest purity in jewelry is often 18K.