I know a friend who can get us free tickets.

我认识一个可以给我们弄到免费票的朋友。

youdao

I know a friend who regrets a choice he made at age 21 (not getting a certain job).

我认识一个朋友，他对于他21岁时做出的一个选择感到后悔(没有得到一个稳定可靠的工作)。

youdao

If you know a friend is waiting for you, you will be less likely to hit the snooze button.

如果你的朋友在等你，你将不那么容易选择按下暂停开关。

youdao

"Know that America is a friend of each nation and every man, woman and child who seeks a future of peace and dignity, and we are ready to lead once more."

VOA: special.2009.01.24

The master had commanded his servants, of course, to do something - to show a profit in a due and timely fashion, but Milton wants his friend here to know that there's, of course, nothing to worry about.

主人要求他的仆人，适时的,展示出自己的利润，弥尔顿希望，他的朋友知道。

耶鲁公开课 - 弥尔顿课程节选

And you friend says, "Well, you know I was kind of a nerd in high school. No one really liked me."

你的朋友说“呃，你知道，我在高中时是个书呆子。没什么人喜欢跟我打交道。”

I used to 课堂 - SpeakingMax英语口语达人

You may know a friend or a family member whose life was turned upside down because of some of these unsavory practices that this agency is designed to root out, and maybe you were then determined to prevent that from happening to somebody else.

WHITEHOUSE: President Obama Speaks at the Consumer Financial Protection Bureau | The White House

The American people know that we have a great friend in the people of Panama and we hope that the people of Panama know that they have a great friend in the United States of America.

WHITEHOUSE: President Obama and Panamanian President Ricardo Martinelli | The White House

Often we accept people into our social networks by extension of trust, i.e. a friend of a friend, so a good rule of thumb might be to question how well you really know a person before accepting a new friend request.

FORBES: Be Careful Who You Know