主因

zhǔ yīn wèi xiáng

主因未详。

The details of the principal cause are not known.

hòu tiān de yīn sù shì yòu fā ái zhèng de zhǔ yīn

后天的因素是诱发癌症的主因。

Acquired factors are the main reasons for the onset of cancer.

jiāo ào zì mǎn shì tā xué xí chéng jì xià huá de zhǔ yīn

骄傲自满是她学习成绩下滑的主因。

Self-conceitedness is the main cause for the downslide in her studies.