请教英语中副词后接副词的情况及意义!

he went downstairs fast.
他飞快的下了楼。

不能光看两个副词在一起有什么意义，要看副词修饰的是哪个动词。
downstairs adv. fast adv. 都是副词，用来形容went。

example: I study English REALLY HARD, but I don't speak that language VERY WELL.
--- The first adverb modifies the second.

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百度百科里面有介绍，上面的网址，去看一下：）