long before
很早以前
before long
adv.
不久以后
before long(=soon)与long before的区别：before long“不久”、“很快”,用于各种时态.例：We'll meet again before long.long before是“很久以前”,单独使用,一般用在过去完成时的句子里.例：They said they had seen the film long before.同时,long before后可以接从句.I had seen the film long before you saw it.