What is the cause of lenght ,width and depth?

Answer 1

Orthogonality.

Specifically, the ability to move in a direction without moving in any other. This does not depend on the measuring system or labels you use.

We have three orthogonal spatial dimensions and one orthogonal temporal dimension.

Answer 2

I'm not exactly sure what you mean. Do you mean, "Why do we regard length, width, and depth as the definition of an object's size?" It's because we exist in three dimensional space, and it takes three linearally independent vectors to define a three dimensional object. It is very convenient to use an orthogonal basis, in which each of the three vectors is perpendicular to both of the others, so we've established length, width, and depth as a conventional system to refer to that basis.

Answer 3

perception