A copy is any duplicate, reproduction, or imitation of an original. A replica is either a) an exact copy produced by the original artist or manufacturer, or b) a copy made at a smaller scale than the original, i.e., a model.
请看上面的英文解释。
也就是说copy可以表示假的复制品。
而replica一般真品。比如一个产品可以做很多一样的,然后卖。