not … until… / not until… / It was not until… that
实战翻译：
1. 直到会议快要结束时他才露面。 （show up）
2. 直到二十世纪初人们才学会怎样防止这种疾病的蔓延。 (prevent)
3. 直到那时他才意识到他的老师是非常善解人意的。 （considerate）
4. 可惜他们直到事故发生之后才采取措施防止它。
5. 直到上周末收到你的来信时我们才如释负重。 （relieve）
答案如下，如果你都能轻松做对了，恭喜你，请滑走：
1. Not until the meeting was almost over did he show up.
2. Not until the beginning of the 20th century did people learn how to prevent the disease from spreading.
3. Not until then did he realize that his teacher was very considerate / thoughtful / understanding.
4. it’s a pity that they didn’t take any measures to prevent the accident until it happened.
5. Not until we heard from you last week were we relieved.
解说：
深刻理解“not……until”的三种句型
陈述句
"not...until"的基本陈述句结构是：“主语 + (not)动词 + until + 从句（或是表示时间的词）”。
例如：
I didn't go to bed until my parents came back.
直到我的父母回来，我才去睡觉。
Man didn’t know what heat is until the early years of the 19th century.
直到19 世纪初，人类才知道热能是什么。
Until 直到….为止, not… until直到…才
肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的。
否定形式表达的意思是"直至某时才做某事"。动词为延续性或非延续性都可以。
肯定句：
I slept until midnight. 我一直睡到半夜时醒了。
Wait till I call you. 等着我叫你。
否定句：
She didn't arrive until 6 o”clock.她直到6点才到。
Don't get off the bus until it has stopped.公共汽车停稳后再下车。
I didn't manage to do it until you had explained how. 直到你教我后，我才会做。
否定句可用以下两种句式表示表示强调：
倒装句
"Not...until"的倒装句结构是：“Not + until +从句（或是表示时间的词）+助动词/情态动词 + 主语 + 动词”。
例如：
Not until my parents came back did I go to bed.
直到我的父母回来，我才去睡觉。
Not until the early years of the 19th century did man know what heat is.
直到19 世纪初，人类才知道热能是什么。
强调句
"Not...until"的强调句结构是：“It is/was + not + until + 从句（或是表示时间的词）+that+主句”。
例如：
It was not until my parents came back that I went to bed.
直到我的父母回来，我才去睡觉。
在这个句子中，“It is/was”是强调句的引导词，直接强调not until +从句my parents came back”这个时间状语从句。
It was not until the early years of the 19th century that man knew what heat is.
直到19 世纪初，人类才知道热能是什么。
三种译法比较：
He did not know the truth of the matter until a few months later.
Not until a few months later did he know the truth of the matter.
It was not until a few months later that he knew the truth of the matter.
直到几个月后，他才知道事情的真相。