Be familiar with sth/sb

（某人）很了解某人/通曉某件事情

to know something or someone well

John is very familiar with software development. He’s been working in IT for 20 years.

John很了解軟件開發。他做IT已經有20年了。

I am not very familiar with Han. We’ve just met once.

我對Han不是太了解。我們只見過一次。

Know 認識(程度可深可淺)

Do you know Penny (well)?

你認識Penny嗎？

Acknowledge

(通過招手、微笑等) 打招呼/示意

I was standing right next to her, but she didn't even acknowledge me.

我就站在她身邊，但她根本就沒有向我打招呼。

Be familiar to sb

(某事)對某人來講熟悉

似曾相識/見過/聽過/聞過

The name of the restaurant was not familiar to me.

I didn't know the name of the restaurant.

這個餐館的名字我沒聽過。

Acquaintance /əˈkweɪntəns/ n.

泛泛之交；熟人

I heard about the job through a mutual acquaintance.

我是從一個朋友的熟人那了解到這個工作機會的。