为什么 if i were a boy 中的were 不用was?

在虚拟语气的从句中，动词'be'的过去时态一律用"were"，不用was， 即在从句中be用were代替。
If I were you, I would go to look for him.
如果我是你，就会去找他。
If he were here, everything would be all right.
如果他在这儿，一切都会好的。

虚拟语气中，if引导的从句部分,与现在事实相反，be动词一律用were，不考虑主语。与过去事实相反，用had done；与将来事实相反，也是用were.

这是虚拟语气，一般系动词用were而不用was

虚拟语气里 be 动词 一律变为 were 这个是常规
记住就行了

虚拟语气啊

虚拟语气，规定此处用were,因不是真实的。

是虚拟语气，虚拟语气中的was必用were，表示事实与假设相反。例如，If I were you,I would go.（如果我是你，我就去。）我不可能是你，与事实相反。

The subjunctive mood,always weak in English,has been dwindling away for centuries until it has almost vanished.According to traditional thought,statements about the conditional future such as “If I were a carpenter ...” require the subjunctive “were”; but “was” is certainly much more common.Still,if you want to impress those in the know with your usage,use “were” when writing of something hypothetical,unlikely,or contrary to fact.
The same goes for other pronouns:“you,” “she,” “he,” and “it.” In the case of the plural pronouns “we” and “they” the form “was” is definitely nonstandard,of course,because it is a singular form.

这是虚拟语气中的规定，这里有if证明是虚拟语气，而在这种语法现象中原来的be动词都要变为were,不管主语是什么！