什么叫连接代词？所谓连接代词，指的是用于引导名词性从句或不定式的代词。
1. 引导名词性从句的连接代词：比较常见的有 what, which, who, whom, whose, whatever, whoever, whomever, whichever等。如：
It is clear enough what he meant. 他是什么意思很清楚。(what引导主语从句)
Ask him which he wants. 问他要哪一个。(which引导宾语从句)
The problem is who can be put in charge of the work. 问题是谁能来负责此事。(who引导表语从句)
Whoever comes will be welcome. 任何人来都欢迎。(whoever引导主语从句)
Buy whichever is cheapest. 买最便宜的。(whichever引导宾语从句)
I’ll just say whatever comes into my head. 我将想到什么说什么。(whatever引导宾语从句)
2. 连接代词除用于引导名词性从句外，有时也可引导不定式。如：
I ask him what to do. 我问他该怎么办。
Show me what to do. 给我说说该做什么。
Did you ask her which to buy? 你问没问她该买哪一个?
He doesn’t know whom to believe. 他不知该相信谁。
这类用法通常可视为名词性从句的省略。如：
I wonder who to invite. =I wonder who I should invite. 我拿不定该邀请谁。