根據Oxford dictionary:
whoever
pronoun
huːˈevə(r)
; huːˈevər
; huːˈevər
1 the person or people who; any person whoWhoever says that is a liar.Send it to whoever is in charge of sales.2 used to say that it does not matter who, since the result will be the sameCome out of there, whoever you are.I don't want to see them, whoever they are.3 used in questions to mean ‘who’, expressing surpriseWhoever heard of such a thing!
這幾個人很哈人用.
首先, whatever, whichever, whoever 相同之處是它們均可引出主詞子句,受詞子句, 介系詞受詞子句 (或叫名詞性關係子句, nominal relative clause; see CCEG*), 和讓步副詞子句.
引出主詞子句:
Whatever
you do is right.
你做什麼也是對的.
Whatever
you do是句子中的主詞 (subject),
同時也是子句(clause).
引出受詞子句:
I will do whatever is necessary.
引出介系詞受詞子句：
Send it to whoever is in charge of sales.
作讓步副詞子句：
Come out
of there, whoever you are.
而幾個字的不同在，whatever和whoever在子句中都是名詞，但whichever 在子句中是形容詞：
Either
Thursday or Friday - choose whichever day is best for you.
whichever
day is the best for your是受詞子句。
當然，若whichever連用的名詞在前文後理很清楚，可以不寫出來，使whichever形同名詞：
All the
books are here. You can borrow whichever (book) you like.
而whatever也可作形容詞:
She would tell him whatever news he got.
* CCEG: Collins Cobuild English Grammar
