carat / caret / karat
Weight of gems, the proofreader’s mark, and purity of gold.
A carat measures gem weight. A caret is the mark that shows an insertion: ^. A karat measures gold purity: 18-karat gold. Do not write 18-carat gold when you mean purity, or caret for the gem.
Examples
Usea two-carat diamond
Use18-karat gold
UseInsert a caret at the gap.
Avoid18-carat gold (If you mean purity.)