used in expressions of time with the simple past tense to show how far in the past something happened (与动词的一般过去时连用)以前 two weeks/months/years ago 两周/两月/两年以前 The letter came a few days ago. 这封信是几天前寄来的。 She was here just a minute ago. 刚才她还在这儿。 a short/long time ago 不久/很久以前 How long ago did you buy it? 这东西你是多久以前买的? It was on TV not (so) long ago. 电视不(很)久以前播出了这个节目。 Scientists think there was water on Mars a long time ago. 科学家认为很久以前火星上有水。 He stopped working some time ago (= quite a long time ago). 好久以前他就不工作了。 They're getting married? It's not that long ago (= it's only a short time ago) that they met! 他们要结婚啦?他们刚认识不久嘛!
Word OriginMiddle English ago, agone, past participle of the obsolete verb ago ‘pass’, used to express passage of time.