folly
noun uk/ˈfɒl.i/ us/ˈfɑː.li/
(STUPIDITY)
[ C or U ] formal愚蠢；愚蠢的行为（或念头等）
the fact of being stupid, or a stupid action, idea, etc.
She said that the idea was folly. 她说这是个愚蠢的主意。
[ + to infinitive ] It would be folly for the country to become involved in the war. 那个国家要是参战的话实属愚蠢之举。
(BUILDING)
[ C ] UK装饰性建筑（尤指见于英国花园或公园内的小型城堡、殿堂等）
a building in the form of a small castle, temple, etc., that has been built as a decoration in a large garden or park
a Gothic garden folly 一个歌特式的花园建筑