to be aware of, to have a relationship with someone
Past Participle form
I know him.
She knows a lot about the solar system.
A: Hey, do you know much about Shakespeare?
B: No, I don't know anything.
A: Me neither. I have to do a project about him.
B: Better start reading.
I knew her from school but I haven't seen her for ages.
She studied French at school so she knew a lot but she's forgotten most of it.
A: Did you know that Chinese is the hardest language to learn?
B: I knew that because I studied it.
A: Did you get far?
B: Ha! No...
THIS FORM IS NOT USED.
I've known him for years.
My wife has known about my love of chocolate for a long time.
A: Did you know about this book?
B: Yes, I've known about for a while but I haven't read it.
A: Shall we read it together?
B: That sounds fun.