discover: may apply to something requiring exploration or investigation OR to a chance encounter and always implies the prior existence of what becomes known: ~ed the source of the river.


ascertain: implies an awareness of ignorance or uncertainty and a conscious effort to find the facts or the truth: will try to ~ the population of the region.


determine: largely scientific or legal in usage, emphasizes the intent to establish the facts or to  decide a dispute or controversy: unable to ~ the exact cause of the disease.


unearth: implies a bringing to light of something forgotten or hidden: ~ old records .


learn: implies acquiring knowledge either with little effort or conscious intention: ~ed the truth by chance; OR by study and practice: spent years ~ing Greek.


discover发现:可指探索调查发现，或偶然遇见，ascertain确定: 指知道自己不知道不确定，所以有意识去查找真相，determine确定: 多用于科技法律，表示确立事实、解决争议，unearth发掘: 使被遗忘或隐藏的显现出来，learn学习了解: 可表示不费力劳神便获得知识；或通过学习练习


记忆方法: 1）首字母DADUL想成LAUDD赞扬<=发现     本组的词都表示被发现的事物之前已存在  （laud公开赞扬to praise highly and often publicly，如the obituary lauded him as a great statesman and soldier讣告称赞他为伟大的政治家和战士，如her much-lauded rendering of Lady Macbeth她饰演Macbeth夫人，倍受赞誉，如to laud someone to the skies对某人备加赞颂）

         2）发现的意思是找出未知mean to find out something not previously known to one.