Path dependence

Path dependence is a way of saying that it is hard to change something that has already been established. Imagine a path through a park. At the beginning, there's only one path so you have no choice but to walk down it. As time goes on, maybe you and other people who walk in the park add some turns and forks in the path. Now it is really hard to change the path because since so many people have walked it in that way before, it's too hard to make it different. That's path dependence - something starts off in one way, and even if it would be better to change it, it's hard to do that.