我警告他们对此事要守口如瓶。

I've warned them to keep their mouths shut about this.

《牛津词典》

我警告过她无数次了。

I've warned her countless times.

《牛津词典》

我警告过他无数次了。

I've warned him a thousand times.

youdao

So this is Virgil: "When I was fain to sing of kings and battles, the Cynthian god" -that's Phoebus Apollo -- "plucked my ear and warned me."

这就是维吉尔所写的：“我欣然乐意着笔于国王与战争“,“而辛西亚那之神“,即为阿波罗-“在我耳边低声警告我“

耶鲁公开课 - 弥尔顿课程节选

it's like, "Wow, my computer will tell me some warning message or something."

比如，“哇，我的电脑会告诉我一些警告信息或其他东西。”

有这样的困难 - SpeakingMax英语口语达人

As one of my favorite historians warned me once, "Don't leave out the politics."

我最喜欢的一位历史学家曾如此警告过我,"不要忽略了政治"

耶鲁公开课 - 美国内战与重建课程节选