在常用词dialogue，diameter中有个希腊语源的前缀dia-， 它原是个希腊介词，意思相当于through或across。dia-是个原生词缀，它只和希腊词根结合，构成原生词。di-是dia-的异体， 它只用在o，u等元音字母前面。

下面先介绍几个以dia-开头的原生派生词。 

diameter [ dia- = through 穿；meter =measure 测量=>“a measure through the centre 穿过中心的测量长度”→]n. line passing from one side to the other through the centre of a circle 直径 / The diameter of the earth is about 8,000 miles. 地球的直径约为 8,000英里。 

diametral a. 直径的

dialogue [ dia- = across 交叉；logue = speech 说话=> “a speech across or between two persons 两人交叉的说话”→]n. conversation 对话 / Two actors had a dialogue in the middle of the stage.两个演员正在舞台正当中对话。

diagnosis [ dia- = through 通过;gnosis = inquiry 查询=>“a decision through inquiry 通过查询做出的决定”→] n. the discovery of the nature of disease by examining the symptoms 诊断 / The doctor made the diagnosis by using X rays and blood samples. 医生利用X光透视与验血做出了诊断。

diagnostic a. 诊断的 

diagnostian n. 诊断专家