On the Theoretical Progress of the Cognate Words' Study from the Change of the Definitions of Cognate Words

The study of Chinese cognate words emerged at pre-Qin dynasty; but the theory study of it was still weak.The definition of the cognate words was not put forward until modern times.In early times,researchers made definitions from word meanings themselves and sounds,which could not reveal the nature of cognate words.The perfect definitions of cognate words should include the essential characteristics of a group of words which have the same roots and the main characteristics of similar meanings and sounds.The same roots mean they have the same etymological meanings which were the most important thing in judging cognate words.This is a great progress in the theoretical study of cognate words.