A friend has a definition, and I think it’s especially accurate.

What is a friend?
A friend is someone who can double your happiness,
and make your sadness simple.
The older you get,
the more you realize that having a good friend is very rare.
Even if you’re not in the same city,
and you can’t see each other often,
and you’re not always chatting,
as long as there’s someone like this in your heart,
you’ll feel secure.