Friendship is a state of mind.
When I was a kid, I wanted to play with my friends all the time. Being together was a proof of friendship at that time.
Nowadays, my friends are living around the world. We rarely are in the same place. But they are still my friends — no matter where they are.
Even if we haven’t heard each other for years. Even if we might not be able to meet at all for the rest of our lives. Even if they have already passed away.
If we remember them, that’s a proof of friendship.