Polysemy means that one single word has two or more senses at the same time. 它是指一个单独的词同时有两个或更多的意义。

The bulk of English words are polysemantic; one –meaning words are rare and are mainly scientific terms such as hydrogen, molecule, and so on.

1. Two approaches to polysemy

Diachronic approach历时研究方法

It is assumed to be the result of growth and development of the semantic structure of one and same word.一词多义是同一个词的语义结构历史发展的结果。

The first meaning is the primary meaning原始意义. Later meanings are called derived meanings派生意义.

      Synchronic approach共时研究方法

Synchronically, polysemy is viewed as the coexistence of various meanings of the same word in a historical period of time. 从共时的角度看，在同一个历史时期，同一个词可以拥有许多不同的意义。

The basic meaning of a word is called the central meaning 中心意义. The derived meanings are secondary in comparison.

2. Two processes of development

1) Radiation辐射型                              2) Concatenation连锁型

1) Radiation辐射型

Semantically, radiation is the process which the primary or central meaning stands at the center while secondary meanings radiate from it in every direction like rays. 从语义学上讲，辐射型是这样一种过程，在此过程中，本义（也称中心意义）处在中心位置，次要意义从此处象光线一样朝各个方向辐射。

All the meanings are independent of one another, but can all be traced back to the central meaning.这些次要词义之间相互独立，但均可追溯到中心义。For example:

The head of the school, six pence per head, the head of a page, to come to a head, to lose one’s head, six head of cattle.

Though these senses have little in common, they all derive from special application of the central idea of head as a part of the body.

2) Concatenation连锁型

Concatenation is a semantic process in which the meaning of a word moves gradually away from its first sense by successive shifts until there is no connection between the sense that is finally developed and the primary meaning.连锁型是一种语义过程，在此过程中，一个词的意义象链条一样，通过连续的改变，逐渐从本义移开，直至最后发展出来的意义和本义没有了任何关系。

例1：board：木板→餐桌→会议桌→董事会

例2：candidate：穿白袍的人→身着白袍申请职位的人→候选人