to make a particular activity necessary

Obviously what she did was wrong, but I don't think it warranted such a severe punishment. 显然她做得不对，但我认为她不应该受到如此严厉的惩罚。

It's a relatively simple task that really doesn't warrant a great deal of time being spent on it. 这是一个相对来说比较简单的任务，不必在上面花费大量的时间。

See also: unwarranted

used to say that you are certain about something

He's to blame, I'll warrant (you). 是他的错，我（跟你）保证。

an official document, signed by a judge or other person in authority, that gives the police permission to search someone's home, arrest a person, or take some other action

a search warrant 搜查令

Judge La Riva had issued an arrest warrant/a warrant for his arrest. 拉里瓦法官已经签署了一份逮捕状／逮捕他的令状。

a reason for doing something

There's no warrant for that sort of behaviour! 那种行为毫无任何根据！