"Not…until"是英语中常见的短语，表示某事在另一事发生之前不会发生。其用法包括表示时间点或条件，表示情感或态度，以及表示转变或改变。理解和区分这些用法有助于更好地掌握"Not…until"的使用。
用法一
"Not…until"可以用于表示某个时间点或者某个条件。例如：
- I didn't start studying English until I was in high school.
- She won't go to bed until she finishes her homework.
这些句子中，都用了"Not…until"来表示一个时间点或者条件。也就是说，直到这个时间点或者条件满足之前，某件事情都不会发生。
用法二
"Not…until"还可以用于表示一种情感或者态度。例如：
- He didn't appreciate his parents' efforts until he became a parent himself.
- She didn't realize how important her health was until she got sick.
这些句子中，用了"Not…until"来表示一种情感或者态度。也就是说，直到某个时候，才认识到某个事情的重要性或者价值。
用法三
"Not…until"还可以用于表示一种转变或者改变。例如：
- It wasn't until I traveled to a foreign country that I realized how important it was to learn a new language.
- She didn't realize how much she loved him until he was gone.
这些句子中，用了"Not…until"来表示一种转变或者改变。也就是说，直到某个时候，才发生了对某个事情的新认识或者新想法。
