If only I were an Englishman是什么意思?为什么要用were?

If only I were an Englishman是什么意思?为什么要用were? he speaks as if he were an Englishman 这里的 were可以用 为什么If only I were abird.中的were不用was He speaks English as if he were an Englishman.这里的he不是单数吗为什么用 It seems as if he were an expert 为什么谓语动词要用were 而不是was If i were a boy 为什么用were啊 为什么是if only I were you 而不是if only i was you If only I were his wife... if only i were made of 虚拟语气中为什么要用if I were you If I were a boy中,为什么要用were不用was? if I were a boy为什么要用were不用was?求解