葛底斯堡演讲的第一个单词“fourscore”是什么意思?第一句是“ Fourscore and seven years ago our fathers brought forth on this continent,a new nation,conceived in Liberty,and dedicated to the proposition that all men are created equal.”以此看来Fourscore应该是“80”的意思,但英语词典中为什么没有这个单词?如果是分开的两个单词,也不能表达80的意义吧,求教