你所说的没有主语(包括祈使句)实际上都是省略了主语(甚至谓语,宾语)。前提是在说话人双方都能理解的语境条件发生的。除祈使句外,还有以下形式1-who's that?-(it's) Me.2-Will you come tonight-(I will come)Abosolutely!3-How are you?-(I'm) Fine, (I) thank you.