What is a short story?

What is a short story? Is it a short story, comprising less than twenty pages? I think that many people have forgotten the definition of short story. Because, in "Flowers for Algernon", a "short" story, it has more than twenty pages! Which means it is not a short story. A short story is actually a story that is written in less than three pages! Thats why it is called a short story. Ai....