What is one essential element in the story of echo that makes it a myth?

The story of Echo makes it a myth because it seeks to explain a natural phenomenon. 

The story of Echo explains why sounds echo. Echo was cursed to repeat on the last word someone had just spoken. This story explains the natural phenomenon of the echo -- because Ancient Greeks would not have understood what causes sounds to echo, the myth of Echo explains it.

Dogs have been considered man’s best friend for decades! most likely because of their kind and loyal nature. they make splendid companions. their loyalty is beyond compare and after all, a dog is the only thing on earth that loves you more than he loves himself! dogs see us as their friends and leaders, they’ll do anything in their power to ensure your comfort and safety.