连接副词的概念：
连接副词可分为两类，一类是用于连接句子或从句，常见的有therefore, otherwise, however, moreover, still, thus, meanwhile等，另一类是用于引导从句或不定式，主要有when, why, where, how等。 例如：We all tried our best; however, we lost the game.
Tell me when we shall leave.
I do not know how to find him.
连接副词的分类：
连接副词可分为两类，一类是用于连接句子或从句，常见的有therefore, besides, otherwise, however, moreover, still, thus, meanwhile等；
另一类是用于引导从句或不定式，主要的有when, why, where, how等。
连接句子或从句的连接副词：
其性质类似于并列连词，使用时其前通常用分号或句号；若其前用逗号，则通常带有并列连词（如and）：
如：I don't like it; besides, it's too expensive. 我不喜欢它，而且也太贵了。
We all tried our best; however, we lost the game./ We all tried our best. However, we lost the game. 我们都已尽了最大的努力，不过我们还是输了。
注意：有的连接副词（如however等）后通常有逗号与句子的其他成分隔开。另外，有的这类副词还可位于句中或句末：
如：Peter is our youngest child, and we have three others besides. 彼昨是我们最小的孩子，我们另外还有三个孩子。
He may, however, come later. 不过，他也许一会儿就到。
We all tried out best. We lost the game, however.我 们都已尽了最大的努力，不过我们还是输了。
引导从句和不定式的连接副词：
用于引导从句（名词性从句）或不定式的连接副词主要有when, why, where, how等：
如：Tell me when we shall leave./ Tell me when to leave. 告诉我什么时候离开。
I don't know how I can find him./ I don't know how to find him. 我不知道如何找到他。
Where we can get the money is just our problem./ Where to get the money is just our problem. 到哪里去弄这笔钱正是我们头痛的事。
That's why he speaks English so well. 那就是他为什么英语讲得这么好的原因。
注：连接副词why后不能接不定式，如可说：I don't know why I must leave. （我不知道我为什么必须离开），但不能说：I don't know why to leave.