We tried but failed.

我们尝试过，可是失败了。

It is very important to find out why you failed to achieve your goal.

找到你没能实现目标的原因很重要。

I never fail to phone my parents on their birthdays.

我从来不会忘记在父母生日时给他们打电话。

If a store clerk fails to charge us for an item, what shall we do?

如果商店营业员少收了我们一件商品的钱，我们该怎么办？

I never fail to phone my parents on their birthdays.

我从来不会忘记在父母生日时给他们打电话。

I passed history but failed chemistry.

我通过了历史考试，但化学不及格。

Her work was so bad that the teacher had no choice but to fail her.

她考得太差，老师只能给她不及格。

He saw a terrible accident in which a tram's brakes failed.

他看见了一起可怕的事故，一辆有轨电车的刹车失灵了。

His eyesight is failing.

他的视力日渐衰退。

She has suffered from failing health.

她的身体状况越来越差。

When we needed his help, he failed us.

我们需要他帮助的时候，他却让我们失望了。

My memory failed me at that moment.

那一刻我想不起来了。

Words failed me (= I could not express how I felt) when I wanted to express my thanks to him.

当我想要对他表示感谢的时候，不知道说什么好。