Who and what is a friend?

This is a very intriguing question but most people take it as it is. Sometimes after you meet a person a couple of times, you start consider them as having a friendship, be that a shopkeeper, a service person or a colleague from your work with whom you feel comfortable enough to share your time or maybe your money in the first case. But are they truly your friends or just have their own interests in their hearts and are just playing along because they also feel comfortable with you. And it is just not you but also my late father (May his soul rest in peace) use to call somebody with whom he has seen quite a few times a friend. I guess deep in their hearts, they know that actually they are not your friends but for the sake of maintaining a relationship or lack of a better word, they use this special word. Now for me (and I believe a lot of other people) a friend is one you share your feelings, happiness and sorrow, you invite them to your parties and you go to their parties, their kids and your kids play together, in times of need you can borrow or lend money to them and in case of emergencies you feel comfortable to rely on them. You almost know their past and present history and you are proud of their friendship. Friendship is not that it is just made but it is build up over years and last a lifetime. I have friends with whom I have friendship for decades not years and even though they live in different states and have different schedules, I try to keep in touch with them and them with me. That is what I call a friend.