难道: Is it possible that...?; Can it be that...?; Do you really mean to say that...?; "It couldn't be, could it?!"; "Really??" (in questions of surprise)

First, 难道 is an adv We Chinses always use 难道 as the first words of a sentence. It could make your manner of speaking stronger. It means "really" or ."Is it possible that" or "Could it be said that" e.g: "Is it possible that Ashlee's new album is fabulous?" "难道Ashlee的新专辑不惊艳?" This is my first “answer” I wish could help you ；）

难道你不知道这个词是什么意思吗？（意思是你应该知道这个词是什么意思才对啊） 这是一个副词，用来加强反问的语气

难道常用于提出一种猜测，例如： 我打他家的电话没人接，难道他出去了？ 难道 is often used to present a guess, for example: I called his phone number, but no answer. Did he go out?

难道是一个副词，加强反问的语气，比如：“你能学好外语，难道我就不能？” 也就是说“你能学好外语，我也能”用反问加强语气。