政府在必要时可以动用军队。

The government, when necessary, has recourse to the armed forces.

《牛津词典》

那么你是说，这将会坚定美国公众在必要时参战的决心？

So you're saying this will strengthen the American public's resolve to go to war if necessary?

《柯林斯英汉双解大词典》

只在必要时冲厕所：这意味着不要把厕所当作垃圾桶使用以避免浪费水。

Only flush the toilet when necessary: this means to not use the toilet as a garbage to avoid wasting water.

youdao

It's one element like I claimed before it's sorted and so there's no work to be done.

当有1个元素时，在比较前就知道它是有序的,那就没必要再进行比较了。

哈佛公开课 - 计算机科学课程节选

They're interesting biological reasons for that, but certainly it's relevant, and it's important of course for physicians to be aware of this when they're screening overweight people for Diabetes given that excess risk in the women.

这些生理因素很有趣,也很有意义,考虑到女性的患病风险更高,医生们在为超重人群检查糖尿病时,很有必要注意到女性的患病风险

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选