1. 表示递进:what’s more; in addition;besides;more over; last but not least 2. 表示转折:however; on the contrary 3. 表示因果:therefore; thus;because; as a result (of) 4. 表示对比:on the contrary; onthe other hand 5. 表示总结:to sum up; all in all;in a word; in conclusion