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，不定式，主要的有when, why, where, how 等。

1.连接副词起连接两个句子或子句的作用

如: however,moreover,consequently,hence,also,besides,,otherwise,therefore,thus,thereupon等等

I feel a bit tired. However, I can hold on.  我有点累了,但我能坚持下去。

They talked about it for hours. Finally, they decided to go. 他们对此商量了好几个小时,最后他们决定去。

I have never been to Wales. I, therefore, don't know much about it. 我从未去过威尔斯,因此我对它知道的不多。

The weather was cold. Therefore(Thus), we stayed home. 天气寒冷, 因此我们待在家里。
2.连接副词通常位于子句的句首,有时也可位于句中。

(1) They talked about it for hours. Finally, they decided to go。

他们对此商量了好几个小时,最后他们决定去。

finally作为连接副词, 放在句子的句首。

(2) I have never been to Wales. I, therefore, don't know much about it.

我从未去过威尔士因此我对它知道的不多。

therefore作为连接副词,位于句子的句中。

3.有些连接副词的含义彼此相同或相近,在使用时可以互相替换,而不会改变原句的含义。

The weather was cold. Therefore (Thus), we stayed home. 天气寒冷,因此我们待在家里。

therefore和thus的含义相近,因而也可以互相替换。

另一类你应该知道就不说了。