Caret is a mark (^) indicating that something needs to be inserted: “He included a caret, ^, while he was editing the lexicon, whenever it was necessary, to show where something should be added that was missing; such as, a word or phrase.”
For American English, Karat, a unit of fineness for gold, equal to 1/24 of the total amount of pure gold in an alloy: “Pure gold is 24 karat while gold that is 50 percent pure is 12 karat.”