如果头痛只发生在晚上，缺少新鲜空气和氧气常常是其原因。

If headaches only occur at night, lack of fresh air and oxygen is often the cause.

《柯林斯英汉双解大词典》

它通常只发生在彼此非常亲近的人之间，比如夫妻。

It usually only happens between people who are really close to each other, like couples.

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性别对他们来说更为重要，因为亲吻脸颊通常只发生在女性之间，或者一男一女之间，而不是两个男性之间。

Gender matters more for them because check-kissing often only happens between women or a man and a woman but not two men.

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We know that two vehicles are going to come along and not help Tony and that the third vehicle will, because everything, as I say, happens in threes in folklore.

我们知道有两辆车会过来,而且它不会帮助托尼，那么第三辆就一定会，因为，我说过，在民间传说中什么都只发生三次。

耶鲁公开课 - 文学理论导论课程节选

That's a real fluid boundary between the divine and human realms, if you ask me. But it only happens there, in one spot.

这在神族和人类之间可真是一个不固定的界限，如果你问我的话，然而这种情况只在一个地点发生。

耶鲁公开课 - 旧约导论课程节选

The problem only arises if you have an int divided by an int.

这个问题只会发生在,当你用一个整型数除以一个整型数的时候。

哈佛公开课 - 计算机科学课程节选