1 表转折的连接词
but , however , while, yet(语气弱), nevertheless(较强行)

2 表比较的连接词
a 两者不同： on the contrary , however , oppositely in contrast
b 两者相同 ： similarly, likewise

3 表结果的连接词
so thus therefore(不能连句子) hence accordingly consequently(不能连句子) as a result

4 表因为的连接词

because since as + 句子
because of due to thanks to + n （名词）
now that, for that reason