1.know better than to do
是固定用法，意思是：很懂得、明白事理而不至于做某事；知道做某事是错的；懂得不该去做某事；；很明白不至于去做某事；不会愚蠢（糊涂）到去做某事；知道不应该做某事；明白不能做某事
be wiser, better informed, or more sensible than to do or believe sth.
请看经典例句：
You should know better than to behave like that.
你应当明白事理，不该那么不懂规矩。
You know better than to say it.
你懂得这件事是不该讲的。
She knows better than to go alone on such a night.
在这样的夜晚，她不至于连不宜单独外出也不知道。
There are some very obvious phrases that we all know or certainly should know better than to use.
我们都知道或是肯定应该知道有些说法已毫无新意，最好避免使用。
She certainly knows better than to tackle such problems by herself.
她当然明白不能独自去解决这类问题。
You should know better than to go swimming right after eating.
你应该知道饭后不能立即去游泳。
I should know better than to using a weak passcode.我应该知道不能用简单密码。
You ought to know better than to go out without an overcoat on such a cold day.
你应当懂得这样冷的天不穿大衣出去可不行。
I think your sister is old enough to know better than to spend all her money on fancy goods.
认为你的妹妹已经足够大了应该明白不至于把所有的钱花在高档商品上了。
She knew better than to argue with Adeline.
她很聪明不至于和阿德林争论。
She should know better than to spend all money on books.
她应该明白不能把所有的钱都花在买书上。
I knew better than to question his decision.
我不会糊涂到去质疑他的决定。
You know better than to talk with food in your mouth!
你不会愚蠢到嘴里喊着食物谈话吧！
He knew better than to interfere in our affairs.
他明白事理不至于干涉我们的事。
I knew better than to lend him any money.
我知道不应该借给他钱的。
Of course, she knew better than to say this to her husband.
当然，她可没有蠢到把这些告诉她丈夫。
They know better than to mutiny against an authority as great as that held by Captain Bligh
他们不会愚蠢到背叛像布莱上尉这样伟大的权威。
We had a row about it last night it was my fault, l should know better than to argue the toss with him late at night.
昨晚我们吵了一架，都是我的错，我应该知道不该在深夜和他争论这个问题。
Eva knew better than to interrupt one of Mark's jokes.
伊娃知道不应该打断马克的笑话。
You should know better than to behave like that.
你应该知道不能那样做。
He knows better than to judge by appearances.
他明白得很，绝不会凭表面现象来判断。
You should know better than to run out into the traffic.
你应该知道，不该跑到车流里去。
He knew better than to talk back to his father.
他知道和他父亲顶嘴是错误的。
I know better than to try and change your mom's mind.
我知道试图改变你妈妈的想法是错误的。
She knew better than to argue with Adeline
她不至于和阿德琳发生争执。
One knew better than to swallow that.
人不会愚蠢到吞下那东西的。
You know better than to be late.
你不应该迟到的。
I had had a marvelous steak, but knew better by now than to say so.
我吃了一块香喷喷的大牛排，但是此刻我明白我还是不说出来为好。
有时谓语部分是should have known形式，表示过去的时间。意为“本应知道不该做(但却做了)”。例如:
You should have known better than to talk like that.
你本应更懂事而不致说这样的话。
Tom should have known better than to ask Dick for help.
汤姆本应该不会糊涂到去向迪克寻求帮助的。
Mary should have known better than to accept a lift from a stranger.
玛丽本应知道不该搭乘陌生人的车。
He should have known better than to believe me.
他本应该知道不该相信我的话。
He ought to have known better than to run away from school.
他本应该懂得不该逃学了。
其至连than后的to不定式偶尔也有用完成体的。例如:
I should have/might have known better than to have asked you for money!
我本来应该知道不该向你借钱的。
2.注意：Sb know better表示某人不相信前面的人说的话：
My sister still claims she cheated on us at cards, but I know better.
我妹妹仍然说她和我们玩牌的时候捣了鬼，其实我心知肚明。
The experts, who knew better, laughed at the idea.
专家们不信这一套，嘲笑了这种说法。
