大家一定还记得拉丁前缀bi-吧。现在要介绍的di-是与bi- 同义的希腊语源的前缀，它的意思也是twice, two。其实，di- 与bi-在印欧语中是同源的。di-最早出现在希腊语源的借词中，只与希腊词根缀合。但在现代英语中，成为很有用的术语前缀，可以跟单词相结合，构成科技术语，尤其是化学术语。

先介绍几个常见的以di-开头的原生词。

diarchy [ di- = two 二 ； arch = ruler 统治者；-y n. = the state 状 态=> “the state of having two rulers 有两个统治者的状态”→] n. government in which the executive power is vested in two rulers (执政权授予两个统治者的）两头政治/ San Marino has a government of diarchy.圣马力诺政府实行两头政治。

digamy [ di- = twice 两次；gamy = marrying 结婚=>“marrying twice 结婚两次”→]n . second marriage 再婚 / Digamy refers to marriage after the death of the first husband or wife, so it is different from bigamy which is unlawful.再婚指失去第一个配偶后的嫁娶行为，它不同于重婚，重婚是非法的。

digamist n. 再婚者 

digamous a. 再者的

digraph [ di- = two 二; graph = letter 字母→]n. two letters used together to spell a single sound 读单音的两个字母 / In the word“each”，“ea” is a digraph. 在 each 这个单词中，ea 两个字母发一个音。