1) What brought on the illness is not clear.
病因未详。
2) The details of the principal cause are not known.
主因未详。
3) an open verdict
死因未详的裁决
4) He didn't go on account of his illness.
他因病未去。
5) Little known species
未详知种
6) Not knowing the details
未知其详
补充资料：主因
1.主要的原因。
说明：补充资料仅用于学习参考，请勿用于其它任何用途。
参考词条