Is there such a thing as breaking up with a friend?

I was just wondering about this. Is there really such a thing as breaking up with a friend or do you just let the friendship fade out slowly? Or simply just cold blooded ignore them?

If you’re in a friendship, but you often walk home with a bitter taste in your mouth, what can you do?
Does a friendship go up and down? Is it important to try to make the friendship better and keep working on it?

Have you been in a situation where you had to end a friendship and how did you do it? What if this friend is also friends with a lot of your ofter friends and what if you’re going to see this person almost everyday?

Merely a hypothetical question.