This article is intended to use the theory of prototype categories to illustrate the four ways of lexical change: generalization,specification,metaphor and semantic shift in terms of the interrelation of "words" and "categories".

The word meaning evolution should be studied both synchronically and diachronically,since a survey of word meaning evolution from the ancient times will easily show that it is not as simple as only in the ways of expansion,narrowing,and shift.

It is also a main approach of changing of words meaning.

An analysis of the causes and types of semantic changes helps English learners better understand the nature of the language.

With the development of modern linguistic theories, in recent years, semantic change has become a central issue again in many fields such as semantics, pragmatics, cognitive linguistics, sociolinguistics, etc.