karat

the word 'karat' entered english in the late 15th century from middle french 'carat', which itself came from medieval latin 'carratus'. these terms trace back to arabic 'qīrāṭ', meaning a small weight or bean pod, borrowed from greek 'keration' (a small horn or carob seed). the greek term is a diminutive of 'keras' (horn), referencing the shape of the carob seed which was used as a standard weight. the semantic journey moved from a specific seed used as a weight, to a unit of weight for gems, and finally to its modern, specialized meaning as a measure of gold purity, distinct from the 'carat' used for gem weight.

this word is a loanword and is not productively segmented into meaningful morphemes within modern english spelling.