warn：
v. 提醒注意(可能发生的事);使警惕;劝告(使有所防备);警告;告诫
第三人称单数： warns
现在分词： warning
过去式： warned
过去分词： warned
例句：
The computer is programmed to warn users before information is d.
这台计算机编程时已设计在信息删除前提醒用户。
People were swimming in the ocean despite the hurricane warning.
尽管有飓风警报，人们仍然在大海里游泳。
She was warned that if she did it again she would lose her job.
她被警告说如果她再这样做就会丢掉工作。
He called out a warning from the kitchen.
他在厨房里大声发出警告。
She had ignored the warning signs of trouble ahead.
她没有理会警示前方危险的标志。
Doctors issued a warning against eating any fish caught in the river.
医生发出警告不要吃在那条河里捕的鱼。