“a six-storeyed building”还是“a six-storey building”?为什么？

“a six-storey building”.因为six-storey 加了连字号-,本身便是一形容词,不用再加ed变为形容词.

后者，名词修名词

“a six-storey building” 是正确的。

也可以说：“a six-storied building”，
但“a six-storeyed building”则肯定不对的。

a six-storey building 或者 a six storeys building