1.
what可用作主语【这时作单数看待】、补语、宾语、介词宾语或定语　　例what（做主语）astonished you?
　　what has(不用have)happened?
　　what(作补语)is the diffrtrnce?
　　what is this man?
　　what（作动词宾语）do you want　　2.
what可用作副词，表示“到什么程度”　　例 what does this small thing matter?