否定副词：never、hardly、scarcely、rarely、seldom、little
否定副词短语：by no means,in no way,on no account,only+介词短语,only…then,not only…but also,only when,not until,no sooner…than
例1：Never is he happy（他从不快乐）
例2：By no means is he the person we need（他绝对不是我们需要的人）
例3：Not only does he do well in his lessons, but also he often helps others with their lessons.
