not until 和unless的区别 我怎么觉得意思都差不多呢

not until 和unless的区别 我怎么觉得意思都差不多呢

直到走投无路才攻击人类 和不攻击人类除非是走投无路

前者 用not .....until强调 时间 什么时候才攻击人类？
后者 用unless 强调条件 什么情况下 才不攻击 人类？
两句意思 虽然一样 但 着重点 不同

not untill是指直到...才 unless指除非

not until是直到什么才，unless是除非。意思不同。

当Not until位于句首时,句子要倒装。其结构为:Not until+从句/表时间的词+助动词+(主句)主语+谓语+...。如: 　　①Not until the teacher came in did the students stop talking.直到老师进来学生们才停止讲话。 　　②Not until next week will the sports meet be held.直到下周才开运动会。 　　2. not until的强调结构为:It is / was not until+从句/表时间的词+that+...。上面两句改为强调句为: 　　③It was not until the teacher came in that the students stopped talking. 　　④It is not until next week that the sports meet will be held. 一、作为从属连词含义不同,引导从句性质不同 unless与until均为从属连词,unless表“除非”,强调条件,引导条件状语从句;until表“直到”,强调时间的延续,引导时间状语从句。 1. I didn't know the news until my teacher told it to me. 2. I couldn't know the news unless my teacher told it to me. 3.—Was his father very strict with him when he was at school? —Yes. He had never praised him until he became one of the top students in his grade. 析:句1动词didn't know表明该句强调时间的延续,表“我不知道这消息”的状态一直延续到“老师告诉我”,因此应用until引导时间状语从句。句2动词couldn't know表明该句强调条件,表“我不可能知道这消息,除非老师告诉我”,因此应用unless引导条件状语从句。句3表明“他爸爸从来没有表扬他”的状态一直延续到“他变成年级最好的学生之一”,因此也应用until引导时间状语从句。 二、作为从属连词引导的从句常用一般现在时表示将来 unless引导的条件状语从句和until引导的时间状语从句常用一般现在时表示将来。 例1:除非邀请你否则别进来。 误:Don't come in unless you will be invited to. 正:Don't come in unless you're invited to. 例2:除非他来,我们不可能去。 误:Unless he will come, we won't be able to go. 正:Unless he comes, we won't be able to go. 三、作为从属连词引导的状语从句可转换为省略式创新句型 unless引导条件状语从句和until引导时间状语从句时,如果主从句主语一致(或主从句主语不一致,但从句主语为it),从句谓语部分含有be,可将从句主语和动词be省略,构成省略式创新句型。 例1:I won't come to see you unless I am asked to. 除非你邀请我,我才会来看你。 析:因为主从句主语一致,从句谓语又含有am,所以可将从句主语I和动词am 省略,构成省略式创新句型:I won't come to see you unless asked to. 例2:The soldiers will not cross the river unless they are ordered to. 除非接到命令,战士们不会过河。 析:因为主从句主语一致,从句谓语又含有are,所以可将从句主语they和动词are省略,构成省略式创新句型:The soldiers will not cross the river unless ordered to. 注意: until也可作为介词。例如: I have remembered her until now. 直到现在我还记得她。