摘要：He did not join them until long after they had eaten. (直到他们吃了很久，他才加入他们。) [牛津高级学者辞典]

long的典型用法是形容词，含义是“长”。

不过，它也可以用作副词，修饰after/before/ago。如

【例句1】He did not join them until long after they had eaten. (直到他们吃了很久，他才加入他们。) [牛津高级学者辞典]

【例句2】The railway had obviously been built long after the house. （这条铁路显然是在房子建成很久之后才修建的。）[柯林斯高级学者辞典]

【例句3】He retired long before the war.（他早在战前就退休了。） [牛津高级学者辞典]

【例句4】This all happened long before you were born. （这一切都发生在你出生之前很久的过去。） [朗文当代英语词典]

【例句5】 It wasn't long before (=soon) Lisa arrived. （不久，丽莎来了。 ）[朗文当代英语词典]

【例句6】It wasn't long before she had persuaded him (= it only took a short time). (不久她就说服了他。)[牛津高级学者辞典]

【例句7】He should have left her long ago. （他早就应该离开她了。） [朗文当代英语词典]

【例句8】I learned long ago to avoid these invitations. （我很久以前就学会了避免这些邀请。）[柯林斯高级学者辞典]

【例句9】The house was pulled down long ago. (这房子很久以前就被拆掉了。) [牛津高级学者辞典]

【例句10】Not long ago (= quite recently) phones were only used for speaking to people or maybe sending texts.（不久前，手机只用于与人交谈或发送短信。） [牛津高级学者辞典]

注意套词 long, long ago(很久很久以前)的第一个long后面有逗号。

来源：擎苍教育