Is it ensure, insure, or assure?
a measure of the fineness (i.e., purity) of gold. It is spelled carat outside the United States but should not be confused with the unit used to measure the weight of gems, also called carat. A gold karat is 124 part, or 4.1667 percent, of the whole, and the purity of a gold alloy is expressed as the number of these parts of gold it contains. Thus, an object that contains 16 parts gold and 8 parts alloying metal is 16-karat gold, and pure gold is 24-karat gold.