since

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【释义】：

ad．❶ (与完成时连用)后来，以后：This city was laid flat by U．S．bombs twenty years ago and has since been rebuilt．这座城市二十年前被美国炸弹炸成平地，后来重建了．He joined the army last year and has not been home since．他去年参军以后还没有回过家．ever since 从那时起，一向：He went to Tibet in 1970 and has lived there ever since．他在一九七〇年去西藏，以后就一直住在那里．❷ (与一般时连用)以前(=ago)：a moment since 一会儿以前．How long since is(or was)it?那是多久以前的事呀?It happened many years since．这是在好多年前发生的．

－prep．(谓语用完成时)自从…以来，自从…以后：The people’s livelihood has been greatly improved since the liberation．自从解放以来人民生活大大改善了．Ssince last talking with you I have been studying the subject．自从上次和你谈话以来，我一直在研究这个问题．since then后来，从那时以来．

－conj．❶ (主句谓语用完成时)自从…以来：We have learned a lot since we came down to the countryside．自从下乡以来我们学到了很多东西．❷ (主句主语为it，谓语用一般时)…以后(已有…时候)：How long is it since you were in Peking?你离开北京已经有多久了?It is four years since we parted．我们分别到现在已经有四年了．It was two years since we had been in the countryside．那时我们已经在乡下两年了．❸ 既然，由于，因为：Ssince you insist I will reconsider the case．既然你坚持己见，我就重新考虑一下吧．Ssince I was very tired，I went to bed early．因为太乏了，我才睡得早．He must have taken it，since it isn’t here．既然这里没有，他可能把它拿走了．