zapoznany z Englisch:

I'm familiar with the idea

The author assumes that his readers are familiar with certain basic concepts.

I’m not familiar with the language of the country but I can always learn.

Are you familiar with this topic?

if you are familiar with something, you know about it because you have learnt about it or experienced it before

1. Allison, are you familiar with a Dr. Rachel Marsh? 2. Al, are you familiar with the Pinkerton Agency?